The French government today criticized U.S. policy in both Lebanon and Grenada in an apparent effort to distance itself politically from Washington.

Giving the first detailed official report on Sunday's terrorist bombings in Beirut, Prime Minister Pierre Mauroy laid the blame for the recent surge of unrest in Lebanon on what he called the "hegemonic ambitions" of the great powers. He accused the United States as well as Syria and Israel of impeding a negotiated settlement.

Mauroy's remarks, in a statement to the National Assembly, came the day before a meeting in Paris of foreign ministers of the four countries that make up the multinational force in Lebanon. The participants, who will include Secretary of State George P. Shultz and his counterparts from France, Italy, and Britain, will consider western policy in Lebanon following the bombings that killed more than 270 American and French troops.

Mauroy said the agreement negotiated by U.S. special envoy Philip Habib and signed by Lebanon and Israel in May, had taken no account of Syria's regional role and had legitimized an Israeli presence throughout southern Lebanon. He added that France "alone or together with its European partners in the multinational force" had sought to pave the way to a national dialogue through a cease-fire following the clashes in the Chouf mountains at the beginning of September.

The remark implied that, in France's view, the United States was playing no significant role in promoting reconciliation among the factions in Lebanon. The head of the Socialist parliamentary group, Pierre Joxe, later described France as "perhaps the only" power in Lebanon not pursuing expansionist, imperialist, or annexationist aims.

France's efforts to distinguish its approach to Lebanon from that of the United States coincides with criticism here of the U.S. invasion of Grenada and Washington's policy toward Central America. It is important for the Socialist government not to be seen to be getting too close to the Reagan administration--both to preserve its good image in the Third World and for domestic political considerations.

The Communist Party, which serves as a junior coalition ally, mobilized some 5,000 supporters this evening for a noisy demonstration outside the U.S. Embassy to protest the invasion of Grenada. A building of an American computer firm, Sperry-Univac, was damaged overnight in a fire started by anarchists who sprawled anti-Reagan slogans on the wall.

Replying to questions in parliament, French Foreign Minister Claude Cheysson said France would support a United Nations resolution proposed by Grenada condemning the U.S. military intervention. Cheysson said that it was "particularly distressing" that France, as "a close ally of the Americans," should find itself criticizing an injustifiable American action.

In the last decade, French troops have been involved in military operations in Suez, Djibouti, the Comoro Islands, Zaire, Lebanon, Chad, Mauritania, Central African Republic, and Tunisia. But these interventions have been justified by successive French governments on the grounds that they received an invitation from the legitimate authorities or were authorized by the U.N. Security Council.