Mayor Walter E. Washington's press secretary described the mayor yesterday as "outraged" by an unsanctioned effort by political rivals to get the mayor an ambassadorial appointment.

Spokesman Sam Eastman labeled the campaign an attempt by the mayor's "political enemies" to capitalize on rumors of the Mayor's desire for a White House appointment and, in so doing, give an unfair political advantage to City Council chairman and mayoral hopeful Sterling Tucker.

Tucker has not played a direct role in the effort, but has received regular reports on its progress, according to reliable sources. Some of Tucker's strongest supporters are leading the effort. If the mayor should leave office before the end of his term in 1978, Tucker would become acting mayor.

This seems certainly contrary to at least the spirit or the letter of the home rule process - attempting to place someone in office in advance of election to give him a leg up as an incumbent," Eastman said.

"The mayor sees it as an effort by a few politicians to hand-pick the next mayor through a backdoor maneuver and more or less take it out of the hands of the electorate.

"The mayor takes strong exception to any report that he's report that he's anxious to get an ambassadorship and leave office. As far as the Mayor is concerned, the only major decision that's up in the air is whether or not he will run for another term" in 1978, Eastman said.

The Washington Post reported yesterday that since March, Del. Walter E. Fauntroy (D-D.C.) and Robert B. Washington Jr., chairman of the D.C. Democratic State Committee have been spearheading an effort to get the mayor out of city hall and into a diplomatic post.

Fauntroy has discussed apossible appointment with Secretary of State Cyrus R. Vance. And the group has received support and advice, respectively, from Sen. Hubert H. Humphrey (D-Minn.) and Sol M. Linowitz, cochairman of the U.S. team negotiating a new Panama Canal treaty and an old friend of Vance.

But well-placed State Department sources said that the mayor has not been seriously considered to date for any of 30 noncareer diplomatic appointments either already made or soon to be made by the administration.

Fauntroy and Robert Washington are both strong political supporters of Tucker. But Fauntroy, the only one of the participants willing to discuss the effort for the record, denies that it is politically motivated.

Instead, he says it is an attempt to find a job in public service for which Fauntroy believes the Mayor is best suited. Fauntroy said he does not intend to support the Mayor for re-election in 1978, and believes that Mayor Washington would be defeated if he should decide to run again.

On Wednesday, when The Post story was being prepared, Eastman refused to relay questions from a reporter to the mayor, who was at home on vacation. Eastman refused again yesterday to issue any response by the mayor, or to get answers to reporters' questions.

But Eastman finally acknowledged that he had talked to the mayor "at length" about The Post report. "He's outraged," Eastman said.

The press secretary said the mayor is concerned that published reports implying that he would leave office early if an appointment were offered could impair his ability to run the city. But Eastman said he could not flatly say that the mayor would reject a Carter appointment if one were offered.

"It's simply something that he's never sought," Eastman said. "He was elected to serve a four-year term and that's what he intends to do. The mayor has no intention of doing anything other than completing his term and making a decision on whether he wants to seek re-election."

In addition to the present ambassadorial effort, The Post has learned that the mayor's name was submitted to the Carter transition team for possible appointment to one of the federal departments. Also submitted, according to a source on the transition team, were the names of former D.C. Department of Human Resources director Joseph P. Yeldell and Human Rights director James W. Baldwin.

The source, a rankling member of the transition team's talent inventory division - which screened top-level administration appointments - said none of the three names was recommended to the White House for selection as either a cabinet member, deputy secretary or undersecretary, or director of an independent or regulatory agency.