A senior Iranian diplomat and at least four of his colleagues in Washington joined the Iranian revolution yesterday by publicly denouncing Ardeshir Zahedi, their ambassador and the shah's strongest remaining political ally.

Jahar Faghin. the embassyhs No. 3 diplomat and nead of its political section, declared in a letter turned over to the Embassy's charge d'affaires that he and the others would no longer work for Zahedi, whom they accused of "conspiring against the interests and will of the Iranian nation."

In one sense, the dissident diplomats were lining up with the new Iranian government, headed by Prime Minister Shahpour Bakhtiar, who let it be known last week in Tehran that he would shortly replace Zahedi and other ambassadors closely identified with the shah.

But diplomatic sources also saw the move as a final bit of evidence suggesting that the shah's authority has been totally shattered and will not be restored. Such dissent in the past has cost Iranians their careers, at a minimum.

Zahedi was due to return to Washington last night affer spending the past two months in Tehran trying to rally military and political support for the shah. He is thought by State Department officials to be preparing the way for the shah's expected arrival in the United States at the end of the week.

During a stop in Paris, Zahedi told an ABC television interviewer yesterday that he expects the shah to return to Iran in three months. The shahhs opposition is portraying the monarch's departure as permanent.

An Iranian Air Force jet landed at McGuire Air Force Base, N.J., last night, reportedly carrying two of the shah's reportedly carrying two of the shah's children and the mother of the shah's wife, Empress Farah. A State Department spokesman said that several members of the shah's family were reportedly aboard the jet.

Other members of the royal family including the shah's elderly mother, arrived in California on Cec. 29 to stay with the shah's sister in Beverly Hills.

Zadedi, who was once married to the shah's daughter and whose lsvish entertaining has made him one of the most socially prominent diplomats in Washington in recent years, was seen by the White House as a vital link to the shah during earlier stages of the crisis.

President Carter's national security affairs adviser, Zbigniew Brzezinski, was frequently on the telephone to Zahedi in Tehran after the shah appointed a military government Nov. 5.

But it is not clear how the administration will handle the 1ame-duck diplomat now. His constant complaints that the State Department was not supporting the shah strongly enough over the past six weeeks led to conflicts with his U.S. counterpart in Tehran, William H. Sullivan, according to diplomatic sources.

The rebellion within Zahedi's embassy came in the form of a letter of protest signed by Faghih, a first secretary and three lower-ranking diplomats, plus other nondiplomatic embassy personnel, according to Ataollah Shafii, a press officer who signed the letter.

Faghih and the embassyhs charge, Assad Homayoun, could not be reached for comment on the letter, which the dissidents asked be transmitted to the foreign ministry in Tehran. Other embassy officials confirmed Shafii's account.

The move caught other staff members by surprise and left many of them uneasy at the prospect of having to choose between the shah's last government and the incoming and still unsteady Bakhtiar government.

Zahedi's "return to Washington as ambassador will mean the continuation of the conspiracy" against the popular movement, the letter stated, adding that as long as he was ambassador "we shall refuse to carry out our duties at the embassy."

Other staff members said they would wait until they talk to Zahedi to decide whether to continue working.