Sharp words from Iranian opposition

''Your government brought nothing but blood and destruction to our nation. Your greatest achievement is the extension of the cemeteries throughout the country.''

This is the verdict of a small but vocal opposition to Iran's revolutionary government. The statement, contained in a six-page open letter written to the speaker of the Majlis (parliament), has infuriated Islamic fundamentalists in Tehran. And it may have far-reaching political consequences.

The letter is an official statement of the National Liberation Movement of Iran and was written by its leader, Mehdi Bazargan. Mr. Bazargan, a former prime minister who resigned just after the US Embassy takeover in November 1980, is the most vocal member of a small group of opposition representatives in the Majlis.

Though very polite in tone and always referring to the Koran, his text is the staunchest attack ever made by a politician living within Iran against the revolutionary government. ''This is the reign of terror,'' he writes. ''Jails are overcrowded, and you don't make any difference between drinking a glass of water and executing a man.''

Then he attacks members of the government: ''They are incompetent and their foreign policy is just aimed at stirring up the hate of our neighbors.

Many observers in Tehran say Mr. Bazargan and his friends have gone too far. A representative to the Majlis recently compared the Bazargan opposition to the imperial family of the Shah. Said Majlis speaker Hojatolislam Hashemi Rafsanjani: ''Those people are just a trash abandoned by the former regime.''

Rumors spread recently that Mr. Bazargan had been arrested and then released. It seems that committeemen had planned to arrest him but were stopped by a phone call from the private secretary of Iranian leader Ayatollah Ruhollah Khomeini. Mr. Bazargan is one of the founders of the present Islamic regime and a longtime opponent of the Shah.

His prestige, especially among the intellectual bourgeoisie, and his seat in the Majlis will make it difficult for his foes to get rid of him. But the fundamentalists' attacks have become more vitriolic. Documents published by the so-called students who occupied the US Embassy purportedly show evidence of good relations between the National Liberation Movement of Iran and the US government. ''Only for that he should be executed,'' a Majlis representative once said.

Mr. Bazargan has repeatedly said he would stay in the country. He is even said to have declined an offer from the Mujahideen-e Khalq, the urban guerrilla organization, to take him under their protection. He also refuses to resign from the Majlis. His departure could give the signal for a wave of arrests and even executions of his supporters.