Poland today granted workers the right to form independent trade unions, a major concession that is expected to end a crippling wave of strikes. It also could considerably affect the power structure of one of the major communist nations.

Poland's Communist Party Central Committee, the country's highest policy-making body, approved the agreement reached earlier in the day by negotiators in Gdansk, the city hardest hit by the 17-day strike, and workers there and in other cities prepared to return to work on Monday.

No other country in the Soviet Bloc has permitted workers to form unions apart from the official labor organizations that are under the direct control of the ruling Communist Party. Soviet officials have warned against efforts in Poland to diminish the authority of the party, but there was no immediate reaction from Moscow today.

The right to form independent trade unions was the key demand among 21 made by the striking workers. The government had tentatively agreed earlier to several of the lesser demands, and negotiations on others are expected to continue, with strikers returning to work in the meantime.

The agreement on independent trade unions, which will be formed parallel to the official unions and have a voluntary membership, represents a skillful compromise between two extreme positions.

The strikers have agreed not to challenge the foundations of Poland's one-party communist system. But there can be no doubt that it is they who have won the most. Even a week ago, such government recognition of an independent organization to represent workers' interests was considered unthinkable.

The struggle within the government and the Communist Party to resolve the strike has already cost the jobs of a premier and several other high Polish officials, and it has the party leader, Edward Gierek, with a shaky hold on his position.

The resurgence of the workers' strength, with the independent unions as a possible new political vehicle, is expected to cause further reverberations in ruling circles.

The only possible obstacle to an end to the strikes, which were joined by approximately 500,000 workers, is a demand by some strikers that dissidents arrested because of involvement with the unrest be freed. Strike leaders said, however, the authorities have promised to look into the issue.

The agreements concluded today in the Lenin Shipyard in Gdansk and in Szczecin, and industrial city in northeastern Poland, were similar. In addition to conceding what were described as "independent self-governing trade unions," the government agreed that strikers will receive full pay for the period of the strike, that meat and other basic commodities will be improved and that censorship regulations will be modified. Wages and family allowances are to be increased.

The Szczecin agreement also included government promises of improved access to the mass media for the Catholic Church and publication again in Polish of the 1975 Helsinki accord on human rights.

Under the agreements, the new trade unions pledged to recognize the leading role of the Communist Party in Poland's political life and to respect the country's military alliance with the Soviet Union. For its part, the government promised to legalize the right to strike and guaranteed the strike leaders would not suffer reprisals.

At the Lenin Shipyard, the center of the strike, the announcement by Deputy Premier Mieczyslaw Jagielski that the government was willing to recognize the new unions was greeted with a standing ovation by a packed hall of more than 1,000 delegates from 500 factories. Later, both sides joined in singing the Polish national anthem.

Strike leader Lech Walesa, a 38-year-old electrician who organized the first protests at the Lenin yard 17 days ago, was carried by strikers in triumph to address the crowd outside the main gates. Workers pressed him for his autograph on copies of the strike newspaper.

The mood at the yard was one of jubilation mixed with exhaustion. One young worker described the establishment of new trade unions as "a great achievement," adding that it would not have been possible without Walesa's leadership.

Another, older striker commented: "The old trade unions just served the needs of the Communist Party -- not us. They were defending the privileged classes. Now we've got unions that are really independent and can represent our needs. Some workers said they had already resigned from the official trade unions.

The approval of the strike settlement was not unanimous within the interfactory strike committee, Agence France-Presse reported. Many delegates reportedly criticized their leaders for agreeing that the activity of the new unions be limited to the Gdansk region. Walesa reportedly assured the dissidents that the new law on unions would apply throughout Poland once the independence movement had a firm foothold in the Gdansk area, but observers said some of the delegates were unconvinced.

[Another objection reportedly was raised to the wording of the agreement under which "the independent unions recognize the leading role of the Communist Party." "This formula does not please me either. It must be in the next text and you must understand it," Walesa was quoted as telling the delegates. Agence France-Presse said the delegates greeted his explanation with a deep silence.]

After speaking to crowds from the shipyard wall, Walesa told foreign correspondents: "This is a realistic compromise. It's the maxium we could have achieved now. I expect to be busy for the next two months drafting the statues of the new unions."

A member of the strike committee, Andrizej Gwiazda, was quoted on Gdansk radio as saying that the new unions would have their own publications and also a research center to investigate workers' living conditions. He said they would be able to express publicly their views on all decisions affecting workers' lives including wage policy, investments, and long range economic plans.

Jagielski, whose patience and calm approach as a negotiator won praise from workers at the yard, said the government wanted the new unions to be an effective voice of the working class. He also appealed for a quick return to work and for national unity.

The movement for free trade unions in Poland has grown within the period of several years from a tiny handful of dissident activists to a huge and disciplined mass organization. Under the agreement, the interfactory strike committee led by Walesa will become the founding committee of the new union.

After tough police action against Warsaw dissidents who helped the strikers organize and formulate their demands, seven leaders of the dissident Workers' Defense Committee, including their spokesman, Jacek Kuron, have been charged with setting up a criminal organization.

If tried and found guilty under the criminal code, they could be sentenced to up to 10 years' imprisonment. It is also possible that they could be released without being sent to trial, as has happened in the past. The Communist Party newspaper Trybuna Ludu carried a strongly worded attack on the defense committee and another Catholic-oriented dissident group known as Ropco. In a commentary, it accused the dissidents of being guided by antisocialist aims and said it was necessary to break the link between and what it described as "the justified grievances of the working class."

Observers speculated that the move against the Workers' Defense Committee, whose leaders have been in detention for more than a week, was designed partly to reassure the Soviet Union of the Polish Communist Party's determination to maintain its full control. Hints were also dropped in the press of a possible purge of the party's membership of 3 million in an attempt to restore discipline to the organization.

In Gdansk, Walesa raised the issue of the new arrests with the government commission, but did not insist on the dissidents' release as a condition for resuming work. Jagielski assured him he would look into the matter.

Despite its earlier stance ruling out independent unions, the government had been under mounting pressure for some days to settle the strikes quickly. The Gdansk and Gdynia shipyards alone have lost around $200 million as a result of the strike, and yesterday labor unrest was reported in the key industrial region of Silesia in the south.

Silesia is also the political power base of party chief Gierek, whose personal authority was severely weakened by the strikes. Gierek came to power in December 1970 after a similar but less widespread round of strikes toppled the authoritatian regime of Wladyslaw Gomulka.