Iran's new revolutionary rulers intend to hold a national referendum on the country's future form of government within a month, but they have not yet decided what choice the people will be given, a government spokesman said today.

Assistant Prime Minister Amir Entezam said the referendum would "definitely" be held before the Iranian new year, March 21. However, he said he did not know whether voters would be able to choose among different systems of government or simply between a monarchy and an Islamic republic.

The government, under the direction of Shiite Moslem leader Ayatollah Khomeini, earlier indicated the public would be asked to answer the question, "Do you want a monarchy or an Islamic republic?"

Since then a number of Khomeini allies, a substantial segment of the middle class and the emerging Iranian left, have been lining up against what they see as an attempt to limit freedom of choice and an effort to force the Ayatollah's dream of an Islamic republic into existence.

One of the most influential critics of the "yes or no" referendum is Ayatollah Kazem Shariatmadari, the highest ranking religious leader in iran after Khomeini.

In a television interview at his home in the holy city of Qom, the Islamic scholar said it would be better to ask the people, "What kind of government do you want?" He said he had not been consulted about the referendum.

Ali Shayegan, an elderly politician being touted by newspapers as a candidate for the first president of an Iranian republic, echoed Shariatmadari's sentiments.

"No dictatorship of any kind must be established by any side," he said following his return Thursday from 21 years in exile. "People of any ideology must be free to express their views."

In a news conference, Assistant Prime Minister Entezam said Interior Ministry officials were working on the "technical details" of the referendum and had yet to set a firm date. He said both the referendum and a new constitution currently being written by a special committee would be open to free discussion and criticism.

Questioned about reports of separatist agitation in the province of Kurdestan in Western Iran, Entezam said the provisional government opposed Kurdish self rule, indicating that even the demands of moderate Kurdish leaders for autonomy rather than secession would not be entirely met.

He also served notice to self-appointed worker committees that the government reserves the right to appoint the head of various public compaies and institutions.

In another development, a group of nine armed men, apparently members of the Khomeini committee's militia, took over the Tehran offices of International Business Machines. They questioned company officials about possible connections between IBM and the Central Intelligence Agency, the disbanded Iranian secret police, SAVAK, or Israel.

The firm's American employes had already been evacuated and no one was arrested, Iranian company officials said. The guerrillas reportedly told them they would be making similar checks on other American firms they suspected of having such connections.

United Press International reported the following from Tehran:

The radio run by followers of Ayatollah Khomeini accused the Soviet Union today of "seindling" Iran out of its natural gas profits.

Tehran's revolutionary radio reminded businessmen of the koranic ban on usury and warned: "Clearly, nearly all economic activities in countries like ours, such as land speculation, buying, selling and letting apartments as well as unequal deals, especially those concerning imports, are unacceptable to Islam."

The radio singled out the Soviet Union, which it said had "swindled" Iran in its buying and selling of Iranian natural gas when the shah was in power.

"If you take delivery of Iranian natural gas at the border and then, without involving yourself in any processing, resell it there and then for three times the amount you paid for it, then this is a clearcut case of swindling, even if you are the Soviet Union," the radio said.

Until the wave of strikes that helped to oust the shah crippled the oilfields, the Soviet Union was importing 30 billion cubic feet of gas annually from Iran through a 700-mile pipeline.

Thursday, a Khomeini official said Iran's oil and gas contracts were being re-examined and hinted that some of them may be canceled while others would be renegotiated.