Feuding among Iran's political factions broke out again today in disputes over foreign U.S. attorney general Ramsey Clark's private mission to Tehran and the issue of spy trials for the American hostages.

Tehran radio described Clark as "the vilest American agent" to take part in this week's conference on U.S. involvement in Iran and demanded to know why Foreign Minister Sadegh Ghotbzadeh had permitted Clark to participate. w

The radio also accused the Foreign Minister of being conciliatory toward the United States.

Later in the day, Ghotbzadeh, taking a stand that could bring him into conflict with many of Iran's clergymen who dominate the powerful Islamic Republican Party, dismissed the idea of hostage trials as unwise.

"It is the trial of the United States which is important, not of individuals," Ghotbzadeh told a news conference. "I don't think the question of a trial is seriously set forth. Obviously some people have talked about it, but personally, I don't think it is a wise idea."

The 53 American hostages ended their 31st week in Captivity Saturday.

Clark headed a group of 10 Americans who attended the four-day Tehran conference in violation of President Carter's ban on Americans' travel to Iran.

During the conference, which ended Thursday with a resolution denouncing the past U.S. role in Iran, Clark agreed to Iranian President Abol Hassan Bani-Sadr's request that he initiate an inquiry in the United States to publicize government documents showing alleged U.S. interference in Iran during the shah's reign.

Bani-Sadr and Ghotbzadeh have called for an American apology for past actions in Iran as a way to help free the hostages.

At the conference, Clark denounced America's role in Iran, but also told the participants -- nongovernmental delegations from 50 countries -- that the hostage-taking was wrong.

The Tehran radio commentary noted that revolutionary leader Ayatollah Ruhollah Khomeini had refused to allow Clark to enter Iran last November when Carter sent him to attempt to negotiate an end of the hostage crisis.

"We hope this clear departure from [Khomeini's] guidelines which resulted in the participation of the vilest American agent . . . will be explained to the people by the officials," the radio commentary said.

Tehran radio currently is under the direction of supporters of the Islamic Republic Party, which is led by clergymen who have taken a hard anti-American stand in the hostage crisis.

While Ghotbzadeh made it clear in his news conference that he does not envisage a Nuremberg-type tribunal to assess alleged U.S. crimes in Iran, he was also critical of the United States for not releasing information relating to its involvement.

"If this information would have been exposed fully, without prejudice, obviously we would have been in much better shape. At least we would have dealt with the real cause and probably the problem would have been solved by now," Ghotbzadeh said.

[Three members of the American delegation arrived in New York tonight and said U.S. customs officials confiscated all their conference materials. They were not arrested and there was no sign they would be detained.]