Deposed Iranian president Abol Hassan Bani-Sadr declared tonight that the rebels who assassinated Iran's president and prime minister also are aiming for the country's revolutionary Islamic patriarch, Ayatollah Ruhollah Khomeini, and have asked Bani-Sadr in the past for authorization to "finish him off."

Bani-Sadr, in an interview at his heavily protected refuge here, said that despite 500 security guards and antiaircraft guns around the north Tehran house that Khomeini rarely leaves, the Iranian leader is vulnerable and his assassination is "of course" possible. But Bani-Sadr added that he has refused the requests for orders to kill Khomeini and that his assassination would be a tragedy for Iran "because the risk of civil war would be so great."

Despite his refusal, he said the underground resistance to Khomeini's rule is trying to rid Iran of what he described as an increasingly bloody repression that has turned all but 10 or 15 percent of the population against the Shiite Moslem ayatollah whom they once revered as their national savior.

"He is a man who does not know what to do," he said of Khomeini.

Bani-Sadr and the Mujaheddin-e-Khalq guerrilla leader who accompanied him to Paris, Massoud Rajavi, said they have no direct knowledge of who set the explosives that killed President Mohammed Ali Rajai and Prime Minister Mohammed Javad Bohanar. But Rajavi sought to imply that his leftist Mujaheddin rebels were responsible, and Bani-Sadr's declaration that he had vetoed assassination attempts against Khomeini strongly suggested that he wielded at least moral authority over those who conducted the terror campaign against Khomeini's rule.

"They asked me several times for the authority to finish him off," Bani-Sadr said. "I did not accord it. It was not only the Mujaheddin. Others also," he added, without specifying who else sought his authority or when the request was made.

In a telephone interview with The Associated Press, Rajavi said, "I am not informed at this time exactly who planted the bomb. But it was the resistance movement, and I do not deny that the Mujaheddin make up the majority of the movement."

Bani-Sadr's comments came at the end of a long day of interviews to French and foreign reporters who traveled to this riverside town at the edge of Paris's industrial suburbs about 30 miles northwest of Notre Dame Cathedral. For the deposed Iranian leader, 48, the public declarations represent what he believes to be the most effective political action open to him without remaining in Iran and running the unacceptable risk of capture and excecution.

His method is ironically parallel to that adopted by Khomeini after he was expelled from Iran and more than two years ago set up a headquarters in a similar suburb of Paris. Through public exhortations and private contacts to supporters in Iran, Khomeini built up the revolution that toppled the late shah, Mohammad Reza Pahlavi.

Since the French government evacuated most of its nationals from Iran earlier this month, it has allowed Bani-Sadr the same freedom of political action accorded Khomeini, lifting a gag order imposed when the fugitive former president emerged from more than a month of hiding and sought refuge here July 29. About 100 French national police, some wearing bulletproof vests and carrying snub-nosed MAT49 submachine guns, have been assigned to protect Bani-Sadr from potential attackers.

Bani-Sadr and Rajavi insisted today that the bombing could not have occurred without help from inside. Everyone in the building is supposed to be searched every two hours to prevent just such an attack, Bani-Sadr said. This means the deadly bomb could only have been planted with the knowledge of security guards, he added.

Bani-Sadr depicted opposition to Khomeini as a widening circle including some among the Islamic clergymen on whom Khomeini bases his support. Also opposing Khomeini's methods -- described by Bani-Sadr as "savage repression" -- are military officers, enlisted men and businessmen from the Tehran bazaar who played an important role in the shah's demise, the former president said.

"I symbolize another tendency," he added, contrasting his goals with the "religious authoritarianism" of Khomeini. "I symbolize the possibility for Iran to live in liberty and independence, and to stay free and prosperous."

Bani-Sadr said that when Khomeini signed orders deposing him as president June 22, the ayatollah's brother Hassan wrote a letter to Khomeini accusing him of imprudence for which "you will have to answer God." This feeling among Iranian leaders soon will influence Khomeini and pressure him to come to terms with the opposition to his fundamentalist Islamic rule, Bani-Sadr said.

"He will give in, just as he gave in to Mr. Reagan" in releasing the American hostages, he added.

Until he changes, Bani-Sadr predicted, the assassinations will continue in Iran.

Bani-Sadr acknowledged that little can be done to change the course of Iran's revolution unless Khomeini is eliminated or he shifts policies, since Khomeini still exercises tremendous moral authority, and even those who oppose his methods are afraid to oppose him openly.

Explaining their fears and his own flight from Iran, Bani-Sadr underlined the executions estimated at more than 600 since June and said, "Do you understand?"

Bani-Sadr insisted that, despite his experiences of the last several months, Khomeini eventually will seek accommodation. At that time, he said, he will return to Iran to organize elections for a new parliament that will cooperate with him to run the country.

"I consider myself the legitimate president of the country," he added.