The decision by 22 U.S. ambassadors to endorse Sen. Jesse Helms (R-N.C.) for reelection drew sharp criticism from several quarters yesterday, with the principal association of career diplomats calling it "a regrettable failure" of judgment by some of America's leading envoys.

"An active-duty ambassador who engages in partisan politics diminishes the office and undermines his or her own ability to serve the United States abroad," the American Foreign Service Association, which represents 12,000 career Foreign Service officers, said.

Lawrence S. Eagleburger, the No. 3 official at the State Department until last summer, said the ambassadors "showed terrible judgment. It's damned well embarrassing to the Department of State. It opens the door to ambassadors participating in the election every two years."

Administration sources said that Helms' staff solicited endorsements from numerous ambassadors, including several who declined to endorse the senator and complained to the State Department about the approach. Deborah DeMoss, an aide to Helms, confirmed that the Helms campaign had approached many of the ambassadors, but said others had volunteered their support.

DeMoss hailed the endorsements as a political coup and said that the State Department "assured us ahead of time that it was both legal and ethical."

State Department counselor Edward Derwinski, a former Republican congressman from Illinois, told the senator's staff last week that the endorsements would not be improper, DeMoss said. The 22 presidential appointees who endorsed Helms are not career Foreign Service officers and not subject to laws limiting participation in politics by federal employes.

DeMoss said that J. William Middendorf II, ambassador to the Organization of American States, offered to go to Raleigh for the announcement Thursday and has made several trips to North Carolina to aid Helms' campaign against Democratic Gov. James B. Hunt. Others who endorsed Helms are the ambassadors to France, Mexico and Canada, along with former ambassador Faith Ryan Whittlesey, a White House special assistant who DeMoss said is scheduled to campaign for Helms next week.

Several current and former diplomats questioned whether planning for the endorsements involved the use of diplomatic offices, government cables, official travel or other federal funds.

Secretary of State George P. Shultz told all U.S. ambassadors in a cable last March that "no appropriated funds or governmental resources should be used for partisan political purposes."

"We're very concerned about whether U.S. government facilities were used for partisan political purposes in orchestrating this effort," said Dennis Hays, president of the foreign service association. The group plans to seek legislation that would prohibit such endorsements in the future.

Some critics focused on the fact that Helms is a senior member of the Senate Foreign Relations Committee, which confirms ambassadors, and that he would replace Sen. Charles H. Percy (R-Ill.) as committee chairman if he wins reelection and Percy loses.

"Something just doesn't smell right about the ambassadors giving their support to the senators who confirm them," said Rep. Patricia Schroeder (D-Colo.), chairman of a House civil service subcommittee.

Others found it unusual that the presidential appointees were backing a leading conservative who frequently has been at odds with the administration on foreign policy matters.

Helms backed Argentina over Britain in the 1982 war over the Falkland Islands and is a strong supporter of right-wing politician Roberto D'Aubuisson in El Salvador.

William van den Heuvel, who has worked in several Democratic campaigns and was ambassador to the United Nations in Geneva during the Carter administration, said that Helms "has a history of terrorizing people in the State Department and blocking appointments. How does it look when these ambassadors, in their fawning obeisance, endorse him? . . . . They'll be seen as politicians who are on a string and are identified with Jesse Helms."

Van den Heuvel, cochairman of a group of current and former noncareer ambassadors, some of whom endorsed Helms, said any diplomat should resign if he wants to work for a candidate. "I can't think of an occasion when a single ambassador, much less 22, has joined in a partisan campaign," he said.

Helms' aide DeMoss said the endorsements would boost the senator's campaign because "one of Hunt's major tactics has been trying to separate Sen. Helms from President Reagan's policies. This shows that he's in the mainstream of the president's foreign policy and has support all over the world."

The State Department responded to the endorsements Thursday by saying that the ambassadors are not subject to the Hatch Act and that the endorsements were an individual decision.

The March cable from Shultz said that "ambassadors have been discouraged from extensive participation in partisan political campaigns. That tradition was based largely on the historical concept that American foreign policy should be conducted in a nonpartisan manner."

The cable also said that "an employe's official title or connection may not be used on a letterhead, in a publication or otherwise so as to employ the prestige of the government to enhance that of a private organization," including political groups. It reminded the ambassadors "that they are full-time federal employes whose first responsibility is the timely and successful completion of their official duties."

Eagleburger, who had been the State Department's ranking Foreign Service officer, said, "While they can all argue that they didn't violate the letter of that instruction, they certainly violated the spirit. I don't know that ambassadors are paid to play fast and loose with instructions."

Eagleburger said that he "would feel the same way if it were Chuck Percy or Gary Hart or anyone else." He said that while some of the 22 ambassadors are his friends, "I'm surprised at their judgment."

The foreign service association repeatedly has complained that the Reagan administration has given 41 percent of its ambassadorial posts to non-career appointees, compared to 27 percent during the Carter administration.

DeMoss said she was disappointed that the North Carolina press had played down the endorsements. "If Jim Hunt had had just one ambassador endorsing him, it would have been page-one news in Carolina," she said.