A Carter administration appointment in a seemingly low-profile post on the Federal Election Commission has escalated into a major confrontation between the White House and Republican congressional leaders.

House Minority Leader John J. Rhodes (R-Ariz.) said that nothing President Carter has done in office has outraged GOP leaders as much as his appointment last week of Samuel D. Zagoria to fill a Republican slot on the FEC.

Some GOP leaders, he said, think that appointment "could be the equivalent to the loss of 25 seats in the House" because of the "sensitive nature of interpreting elections laws."

"It's symbolic of Carter's relationship with Congress, but this is the worst thing yet," Rhodes added in an interview. "This is the straw that has broken the camel's back."

In naming, Zagonia, a former administrative assistand to Sen. Clifford P. Case, (R-N.W.), Carter ignored three recommendatians [WORD ILLEGIBLE] Rhodes and Senate Minority Leader Howard H. Baker [WORDS ILLEGIBLE]

This they charged in a letter to the President violated on agreement they had made with him Feb. 23 on appointments to bipartism boards and commissions.

[WORD ILLEGIBLE] the recommendations, Rhodes said, "is a violation of the intent of Congress and a threat to the integrity of the election commission itself."

The commission is made up of three Democrats and three Republicans, appointed to staggered, six-year terms. Last March, Rhodes and Baker recommended James F. Schoener, minority counsel to the Senate Rules Committee and Robert P. Visser, an attorney who was counsel to the President Ford Committee, for the $50,000-a-year job.

Carter, however, asked them for a list of at least 10 or 12 names, "I also expect that all of my nominees to the FEC will be generally sympathetic to the aims of the FEC . . . particularly financial disclosure and report requirements and public financing," the President wrote.

The two GOP leaders rebelled against the mention of public financing, which they said "is still very much a subject of national debate," [WORD ILLEGIBLE] initially refused to offer more names.

Zagoria, director of the U.S. Conference of Mayor's Labor-Management Relations Service, was then recommended by five liberal Republican senators, including his former boss Case. White House spokesman Rex Granum said.

When Rhodes and Baker learned of this, they added a third name, former Illinois Congresswoman and Federal Communications Commission member Charlotte T. Reid, who was interviewed for the job by top White House aides.

Carter, Granum said last week had agreed to consider names suggested by GOP leaders, but did not agree to allow them to make the nomination. Baker and Rhodes, he added, made a deliberate decision not to submit a longer list of names.

Rhodes expressed concern about Zagoria's ties to organized labor. He said he feared that the commission, in interpreting election finance laws, "could act in a way to shut off funds to Republicans but allow labor to continue to exert influence."

Zagoria, a registered Republican for more than 20 years, was a reporter with The Washington Post for 10 years before joining Case, and once served as president of the Washingon Newspaper Guild. He was a member of the National Labor Relations Board from 1965 to 1969.