The wives of two of the American hostages appealed to the Republican and Democratic Parties yesterday to adopt moderate positions at their conventions on the 8-month-old U.S.-Iran crisis.

"The United States owes no apology to Iran. We have done nothing morally or legally wrong," Penne Laingen, wife of charge d'affaires L. Bruce Laingen, and Dorothea Morefield, wife of consul gneral Richard H. Morefield, said in letters to leaders of the two parties.

But once the hostages are released, the two women wrote, "The United States' posture toward Iran should be magnanimous and open, respecting their desire to be nonaligned, independent and focused on relations with the Third World and Europe rather than with us."

Neither political party appears inclined to include a detailed position on the U.S.-Iran crisis, in its platform. The GOP, which holds its convention next week in Detroit, is drawing up its platform. The Democrats drafted theirs last month for consideration at their August convention in New York.

Morefield said the letters were aimed at prodding the two parties to take stands on Iran. "We wanted to get our feelings known to the people who are making policy for the two parties," she said. "This is the position we would like to see them take. If they are in disagreement with that, we would like to know it."

The letters also were prompted, she said, by recent calls for a U.S. apology to Tehran or a congressional investigation into past American actions in Iran.

She cited calls made by former attorney general Ramsey Clark, who went to Iran last month in defiance of a U.S. ban on travel there. Relatives of several other hotages also have urged congressional investigation or a U.S. apology.

Laingen, 57, is one of three Americans held at the Iranian Foreign Ministry in Tehran since the Nov. 4 embassy takeover. Morefield, 50, is among the 50 American hostages being held elsewhere in Iran.

In their letters, the two women opposed any congressional inquiry before the hostages" release.

"Congressional investigations into alleged 'past crimes' of the United States in Iran are irrelevant to the hostage issue and should not be undertaken," they wrote.

"If any congressional hearings are to be held, they should be held only after the hostages have returned to tell us what happened on Nov. 4, 1979. Such inquiries should be of a constructive and positive nature to formulate sound and realistic policies in regard to acts of terrorism, the safety of Foreign Service and military personnel abroad, the use of U.S. Marines at our embassies, the future U.S. relationship with Iran and a decisive energy policy."

They called for close screening of Iranian applicants for U.S. visas and strict enforcement of visa regulations. But, they wrote: "We believe there is nothing to be gained in taunting innocent Iranians who have come to this country to flee oppression," and they appealed for "a massive effort at dialogue" with Iranians in the United States.