Supporters of Iran's second-ranking religious leader, Ayatollah Kazem Shariatmadari yesterday threatened to boycott Friday's elections for a 75-member council that is to ratify the country's new constitution.

The Moslem People's Republican Party, which consists of Shariatmadari's followers, accused rival Islamic groups of interfering with its election campaign and threatened to pull out of the voting if the government did not postpone it by three weeks.

The party's criticism was directed at members of the Islamic Republican Party loyal to Moslem leader Ayatollah Ruhollah Khomeini.

The postponement demand, delivered in a letter to the government yesterday, has been rejected by the authorities, and the party has begun meetings to decide its strategy.

The letter said extra time was needed to enable the government "to create the proper conditions of security and freedom for the elections," an allusion to harrassment of moderate and leftist organizations.

In the latest such incident, a rally in the north-western city of Tabriz by the main Iranian Marxist guerrilla organization was reportedly broken up Monmay by Khomeini supporters chanting, "The only party is the party of God."

The 75-member council will have one month to approve a new constitution. The official draft of it was published last month and the final version is to be put to a popular referendum.

An estimated 80 percent of the more than 1,000 candidates in the upcoming elections are Moslem clergymen. In an election message last night, Khomeini advised Iranians to ignore candidates who did not believe in Islam.