Early last year, Peter E. Voss, then vice chairman of the U.S. Postal Service Board of Governors, decided that he wanted to be an ambassador, and obliging White House officials, after scanning the list of pleasant European capitals, told the State Department that they thought the Netherlands was a country well-suited to Voss' ambitions.

The department protested that Voss, who was cochairman of Ronald Reagan's 1980 Ohio campaign, didn't have the best qualifications for representing the United States in a country where it has important strategic and trade interests. But the White House rejected these protests and proceeded with its plan to nominate Voss for the ambassadorship -- until it was discovered that Voss had a prior engagement with a federal judge.

Last May, a major probe of Postal Service contracting illegalities resulted in Voss pleading guilty to charges of expense fraud and accepting kickbacks. He was sentenced to four years in prison and fined $11,000.

Until now, the administration has managed to keep quiet the fact that it almost sent a soon-to-be-convicted felon to represent the United States in an important West European capital. But the incident illustrates what has become an increasingly contentious issue within the Foreign Service.

That is the feeling that the Reagan White House has abused its prerogative to name the president's ambassadors by filling 40 percent of the nation's 148 diplomatic missions around the world with political loyalists rather than career diplomats. Foreign Service officers contend that the White House has unfairly blocked deserving professionals from promotion and devalued the quality of U.S. overseas representation.

The Voss case was not an isolated incident. Within days of his guilty plea, the administration was embarrassed by the forced resignation of William A. Wilson, a political appointee who had been serving as Reagan's emissary to the Vatican. Wilson left after it was revealed that he had engaged in a number of bizarre indiscretions, including a secret 1985 meeting with Libyan leader Moammar Gadhafi at the time the administration was pressuring its European allies to isolate Libya.

Sources familiar with the case said that for reasons never made clear, Wilson, a former oil company executive and longtime friend of Reagan, repeatedly ignored direct orders from superiors in Washington to break off unauthorized contacts with Libyan officials. Instead, they said, he apparently exploited his relationship with Reagan to mislead Italian Foreign Minister Giulio Andreotti into thinking that the White House wanted the Italian government's help in arranging the meeting with Gadhafi.

Another well-connected Reagan loyalist, Faith Ryan Whittlesey, fared somewhat better. She has held on to her post as ambassador to Switzerland, but only after Attorney General Edwin Meese III decided there wasn't sufficient evidence to pursue a criminal investigation of charges that she misused an $80,000 embassy fund raised from private donors and hired the son of one donor for a $62,400-a-year job at the Bern embassy.

The Whittlesey case forced Secretary of State George P. Shultz to decree a ban on future solicitation and use of privately donated funds to cover embassy expenses such as entertaining.

Not all of Reagan's political ambassadors have been embarrassments, of course. Some have performed competently, and at least one -- Arthur F. Burns, former chairman of the Federal Reserve Board -- won high marks from professional diplomats for his skillful representation of the United States during four years in West Germany.Tradition of Noncareer Appointments

Appointees whose qualifications are limited to their connections or the size of their election contributions are not a phenomenon unique to the Reagan administration. Former president Jimmy Carter, who made a special effort to appoint ambassadors of distinction and set up a special review panel to assess their credentials, reserved a number of embassies for Georgia cronies and people who had been generous to his campaign.

Wealth and a willingness to use it have long helped would-be ambassadors win appointments. So have political connections. For example, Julian M. Niemczyk, the ambassador to Czechoslovakia, is a former head of the "ethnic" division of the Republican National Committee and a retired Army officer. To the dismay of the Foreign Service, the White House picked him ahead of Saul Polansky, one of the State Department's most senior and most respected specialists on central and eastern Europe.

Many political appointees have been content to enjoy the ambassadorial life and leave the diplomatic work to their Foreign Service subordinates. However, the Reagan administration also has been noted for a goodly number of political ambassadors who have seemed surprised that the countries to which they are accredited don't do things according to Reaganite precepts and who have not shrunk from publicly scolding foreign governments about perceived shortcomings.

A number of ambassadors over the past six years -- among them John A. Gavin in Mexico, Evan G. Galbraith in France, Paul H. Robinson Jr. in Canada, Curtin Winsor Jr. in Costa Rica and David B. Funderburk in Romania -- have spent much of their time in noisy feuds with the press and officialdom of their host countries and, when Washington tried to rein them in, with their State Department superiors.

Winsor, a business consultant who served for a time in the Foreign Service, became known among Costa Ricans as "the cancer specialist" because of his constant denunciations of the leftist government in neighboring Nicaragua as "a cancer" that should be excised by military intervention.

In October 1983, when the administration was weighing whether to invade Grenada, it wanted to know if the action would be supported by other island states of the eastern Caribbean. However, the ambassador to Barbados and the neighboring islands, Milan D. Bish, a former Nebraska state highway commissioner, was regarded -- as one official who took part in the planning put it -- as "so incoherent and befuddled" that neither the State Department nor the Pentagon was willing to depend on him. So Shultz sent a veteran career diplomat, Francis J. McNeil, on a secret mission to sound out the views of regional leaders.

A year earlier, when the South Atlantic war broke out between Argentina and Britain, Reagan's first ambassador to London, John J. Louis Jr., a Johnson's Wax heir, was traveling in the United States. According to several State Department officials, the department, whose initial inclination was to order him back to his post immediately, was reminded that Louis was regarded by the British as an amiable but utterly ineffectual diplomat. On reflection, the officials said, it was decided that the wiser course was to keep Louis out of London until the crisis had wound down, leaving the diplomacy to his highly regarded deputy chief of mission, career diplomat Edward J. Streator Jr.

In the past, such situations would cause career officers to do little more than grit their teeth and privately remind each other of the famous Foreign Service story about Malcolm Toon, an outspoken retired ambassador who, commenting on Louis' nomination as ambassador to Britain, described him as a man "whose only qualification for the job is the fact that he speaks English."

During a meeting several years ago, the admiral commanding the U.S. Mediterranean fleet told Toon that he wanted to become an ambassador after he retired from the Navy. Toon shot back that after his retirement from the Foreign Service, he wanted to command an aircraft carrier.

The admiral said that was ridiculous, because years of training and experience were necessary to acquire the highly specialized skills necessary to run a carrier. To which Toon replied: "That's how it is with an embassy."

Last November, Ronald I. Spiers, undersecretary of state for management, provoked the ire of the White House staff by making the same point in an unusually blunt speech to the National Academy of Public Administration.

Spiers noted that since 1981, when 75 percent of U.S. ambassadors were career diplomats, the figure had fallen to 60 percent. He added:

"This is a low point for the past four decades. A net reduction of 23 senior positions filled by career personnel since 1981 makes managing the Foreign Service difficult indeed . . . . Recently we have lost a number of superb officers who spent a lifetime preparing for senior appointments, only to see those prospects dissolve at the last minute."

He charged that the quality of many administration political appointees "makes it painful to recognize the lack of respect this implies for our profession" and concluded:

"A disturbing trend is the use of Foreign Service positions for political patronage. I believe this will have a corrosive effect on the career service. Years ago, generals were commissioned on this basis. No one today would argue for appointing a political supporter to command the 24th Infantry Division, although in peaceful times, and with a good deputy, the division would probably survive as well as our embassies."

Elaborating later in an interview, Spiers said: "The White House has made clear that they don't want me talking about this, but it's not really possible to run a rational career personnel system when you don't know how many top jobs will be available for officers to aspire to. I'd almost rather be told that the Foreign Service will get only a flat 50 percent of ambassadorial appointments. Then you'd at least have some parameters to work within.

"I have 25 ambassadors coming up for reassignment this summer -- all of them good people and no jobs for them because 23 more senior positions in the department and abroad are being held by outside political appointments than was the case in January 1981," he said. "The blockage that this creates has a cascade effect down the ranks that's not helpful to retaining younger officers who see a likelihood that their career aspirations will be blocked."

Robert Tuttle, White House personnel director, denied that the Reagan administration had appointed unqualified persons to ambassadorships and insisted that many of the president's political appointees are fluent in foreign languages and have extensive knowledge of the countries to which they are accredited.

"This administration came to Washington to make a difference, and it has been extraordinarily successful in coming up with people who are extremely well qualified to be ambassadors," he said. "They got their jobs because they are qualified and not because they are friends of the president. There are people outside the Foreign Service who know about foreign affairs, and it's not right to infer that appointment of a few well-qualified outsiders should be a cause of poor morale in the Foreign Service."

Americans have been arguing about what makes a good ambassador since 1778, when Benjamin Franklin was dispatched to the French court to enlist the aid that became a major factor in helping the rebellious colonies win independence.

Franklin was the progenitor of a long line of inspired amateurs whose diplomatic skills have been displayed most notably in recent years by men such as W. Averell Harriman, David K.E. Bruce and Ellsworth Bunker -- all outsiders who came to be accepted by the career service as revered figures in the pantheon of American diplomatic history.

In the postwar era, the slimmest pickings for career diplomats before the Reagan administration were in the early 1960s when John F. Kennedy, who had limited regard for the Foreign Service, sought to infuse overseas embassies with new blood from academic and journalistic circles.

But while career officers resented what Kennedy did, they grudgingly acknowledge that many of his outside appointees -- academicians such as Edwin O. Reischauer in Japan and former diplomats such as George F. Kennan in Yugoslavia -- had impressive foreign policy credentials. The difference between then and now, they add, is that the same can't be said for most of Reagan's choices.Distrust of the Establishment

"This administration has been very atypical both in terms of the number of political appointments it has made and its tendency to keep them on long past the point where other administrations would have sent them back to their old jobs," said Diego C. Asencio, a retired diplomat who heads the Una Chapman Cox Foundation, which is devoted to strengthening the Foreign Service.

"It even is atypical in terms of Republican administrations," Asencio added. "Its appointees are not the old eastern establishment Republicans with which the Foreign Service has been accustomed to working, but people with a radical distrust of the eastern establishment and of the Foreign Service."

Career officers who worked under Whittlesey during her two separate tours at the embassy in Switzerland say her problems resulted from what one privately called "a feeling of paranoia that she was surrounded by liberals who were out to get her. If you wrote her a speech on the most innocuous subject, she'd go over every line looking for Marxist influences. She honestly believed that there was no one she could trust except those people she brought into the embassy from outside."

Such suspicions are common among "movement conservatives" who, despite Reagan's hard-line policies, have waged an unrelenting war against the State Department throughout his presidency. The activist part of that campaign has been led most noticeably by Sen. Jesse Helms (R-N.C.), who has delayed Senate approval of scores of Reagan's ambassadorial and departmental nominees in an effort to force more conservative appointments.

In return, 22 of Reagan's politically appointed ambassadors publicly endorsed Helms for reelection to the Senate in 1984, an unprecedented public gesture that caused Shultz to send a cable to all embassies stating that partisan political activity was inappropriate for American ambassadors.

Many intellectual underpinnings of the Helms campaign come from the Heritage Foundation, the conservative think tank whose theories have greatly influenced Reagan's domestic policies.

Foundation analysts concede that they have had much less success in winning serious attention for their foreign policy ideas -- for example, a proposal by James T. Hackett, a former Foreign Service officer, to fill all State Department policy-making positions with political appointees who share the president's "philosophy and objectives" rather than career diplomats "who often have little or no commitment to the political philosophy of his party."

But if Shultz has kept most aspects of foreign policy on a course that is more centrist and pragmatic than the ideologues want, he has had to pay a price by accepting what George S. Vest, director general of the Foreign Service, calls "the larger political role inserted into the system by this administration."Secretary of State's Limited Power

So Shultz has not fought the White House insistence on retaining a large number of ambassadorships as patronage plums. He has generally accepted the tendency of many political appointees to think of themselves as representatives of the president rather than subordinates of the secretary of state.

Usually, when one of these ambassadors has become too difficult to control -- when a Funderburk denounces as hypocritical the State Department's tendency to soft-pedal the dictatorial practices of Romania's communist regime or when a Galbraith publicly lectures France's socialist government -- Shultz has managed over time to ease them back into private life.

However, as John Gavin's five-year tenure at the embassy in Mexico City made clear, Shultz has had to maintain a well-developed instinct about which political ambassadors he could and couldn't fire.

When Gavin went to Mexico in 1981, he was known, like Reagan at an earlier time, primarily as a former grade-B movie actor. The Mexican press sarcastically suggested that an appropriate response would be to send Cantinflas, the comedian who gained international fame in the film "Around the World in 80 Days," as Mexico's ambassador to Washington.

But Gavin did have some qualifications. He spoke near-perfect Spanish learned from his Mexican-born mother, had majored in Latin American economics and history at Stanford and, having worked in Mexico as an actor and businessman, had extensive first-hand knowledge of the country.

More important, he was a close friend of Reagan and of William P. Clark, who served for a time as Reagan's national security adviser. That meant Gavin knew Reagan's political views intimately and, unlike many other ambassadors, had the clout to bypass normal State Department channels and take a problem directly to the White House.

Yet, once he got on the job, Gavin frequently seemed intent on trying to break all the rules of diplomacy by ignoring State Department objections and engaging in name-calling feuds with key officials of Mexico's left-of-center government.

By the time he left in 1985, Gavin often was cited by conservatives as a model political ambassador. In particular, his admirers applauded his pugnacious determination to respond in kind to every Mexican criticism of the United States and to keep matters such as the fight against narcotics trafficking at the top of the Mexican-American agenda.

He was able to do these things, his supporters argue, because he was not a career diplomat concerned with smoothing the sharp edges of policies and messages the Mexicans might not like. Instead, they say, as a certified Reaganite with ties to the inner White House circle, he was able to give the Mexicans a first-hand look at the president's attitudes toward their country.

Nevertheless, a story told in Mexico City indicates that the Mexicans didn't particularly appreciate the experience. At a dinner before his departure, Gavin made a graceful farewell speech. But according to the story, when it came time for a response, the remarks in praise of Gavin came not from the senior Mexican officials present but from Cantinflas -- a sign that the Mexicans hadn't changed their minds in the five years of his tenure about what would have been an appropriate exchange of diplomatic representation. NEXT: Blacks and Women