Senior Polish officials today defended the legality of martial-law decrees that are due to be endorsed retroactively by the Polish National Assembly at a special session next week.

Controversy has surrounded the legal basis for the military crackdown in Poland since the introduction of martial law in the early morning hours of Sunday, Dec. 13, and the establishment of a Military Council for National Salvation. Supporters of the suspended trade union Solidarity have claimed that the decisions, which were made by the 17-member Council of State, are illegal.

The legality of the decrees also has been challenged in a petition signed by at least 120 leading Polish intellectuals and cultural figures that has been circulating in Warsaw for the past few days. Addressed to the National Assembly (the Sejm), it accuses the military government of violating the free will of the Polish nation.

"Apart from the periods of Nazi occupation in World War II and Stalinism, there were never so many overcrowded prisons and camps on our soil as there are in January 1982. Whoever has tried to enslave our nation has always met with resistance and anger," the intellectuals said.

The document was addressed to the Sejm and the U.N. Committee for Human Rights. But, at a press conference today, a member of the Sejm presidium said it had not been received "officially" yet.

The petition echoed in more forceful language a pastoral letter drawn up by Poland's bishops at a meeting in Warsaw earlier this week and scheduled to be read out in churches at the end of the month.

While the government can afford to ignore the appeal of the intellectuals for the time being, it needs good relations with the church if it is to win any popular support. The bishops have shown that they are not prepared to compromise over demands for the release of all detainees, the ending of harassment of people for their political beliefs or trade union affiliation, and the restoration of independent unions including Solidarity.

The government's answer to these demands will be outlined by the premier and martial-law chief, Gen. Wojciech Jaruzelski, in a keynote address to the Sejm on Monday. It is believed that he has chosen this forum for a major statement of policy in an attempt to demonstrate that, despite the military takeover, the Polish constitution has not been suspended.

Attacks on the legality of martial law have centered on the fact that the council of state--a kind of collective state presidency--is not empowered to pass decrees while the Sejm is in session. Furthermore, there is no provision in the constitution for the establishment of a military council to run the country.

At a press conference today, the chairman of the Sejm's judiciary committee, Witold Zakrzewski, admitted that the assembly had been formally in session on Dec. 13 when the decrees were passed. But he added that they had been passed by the Council of State "for reasons of higher necessity."

Zakrzewski said that, under the constitution, only the Council of State had the right to introduce martial law. Since it had this power, he added, it was only reasonable that it also be given the authority to introduce necessary restrictions on the freedom of citizens.

Poland's military rulers seem confident that the martial-law decrees will be endorsed overwhelmingly when the Sejm meets on Monday. Several deputies who had earlier opposed giving the government any extraordinary powers to deal with strikes or law and order swiftly fell into line once martial law was declared.

Monday's meeting of the Sejm will be a crucial test of how much of this spirit has survived martial law. Foreign journalists are to be allowed to attend the session, but, in contrast to the practice of the past year, the proceedings will not be broadcast live.

Instead, edited highlights will be shown on television later.

The petition from the intellectuals said two key points of international law had been violated as a result of martial law: the self-determination of peoples and the abstention from the use of force in solving conflicts. The right of nations to determine their own political status and economic and cultural development is enshrined in both the United Nations Charter and the Helsinki Final Act, the document said.

The protest, which was dated Jan. 15, was signed by many prominent cultural figures including film director Andrzej Wajda, actor Daniel Olbrychski, writer Andrzej Kijowski, lawyer Jan Olszewski, and economist Edward Lipinski.

Several of the signatories already have been detained for brief periods after sending an earlier letter to Jaruzelski.

"The methods used to intimidate and enslave society provoke our indignation and protest. Indignation is also caused by attempts at splitting the nation: setting workers against soldiers and militiamen, worse treatment for interned workers and peasants than for interned representatives of the intelligentsia, and the blockade of information in the entire country," the petition said.

It added: "Our highest concern is caused by the paralyzing of cultural life, of science and education, and the immobilization of the information media."

The bishops' statement warned of a growing "tide of hate, revenge, and vengeance in Poland" that it said could destroy hopes for national reconciliation unless there was a return to "the path of dialogue between the authorities and society."

The letter called for "the prompt release of all interned, the stopping of pressure for ideological reasons, as well as refraining from dismissing people for their beliefs or union membership. In the name of freedom, we call for the restoration of the right of working people to organize into independent, self-governed trade unions." .