The leader of Poland's independent trade union Solidarity, Lech Walesa, went on nationwide television today to counter government allegations that his union is responsible for the country's deepening crisis.

The highly unusual half-hour television broadcast represented a partial concession by the authorities to the union's demands for greater access to the mass media. In his broadcast, Walesa appealed for an end to polemics and for constructive measures to repair Poland's virtually bankrupt economy.

Solidarity and the government still have not reached agreement on television and radio coverage of the union's first national congress, which opens Saturday in the Baltic port of Gdansk. The state television network has offered transmissions lasting up to 3 1/2 hours for each of the three days of the congress, but Solidarity is insisting on editorial control of the broadcasts.

The government offer will be discussed at a meeting of Solidarity's national leadership Thursday.

Control over the mass media is virtually complete in almost all communist countries, and the appearance by Walesa and other Solidarity leaders on a nationwide telecast tonight as well as the nature of the debate over the forthcoming Solidarity congress are signs of the important changes that have taken place within Poland in the past year.

The dispute over control of the news media has assumed particular importance in view of the arguments now raging here over the extent and pace of economic reform. Solidarity has termed the government proposals inadequate to deal with Poland's crisis and wants sufficient television time and newspaper space to explain its proposals.

Tonight, however, Walesa stressed that the union did not wish to take over political power.

"This is not the time for stupid polemics, such as accusing us of wanting to take over political power. We don't want power, we want to serve the community," he said.

Solidarity had to meet the expectations of ordinary people who had lost trust in the government and now looked to the union for solutions to Poland's problems, he added. It was for this reason that access to the news media was so important.

Central to the present debate between Solidarity and the government are differences over self-management in industry. The union believes the only way to overcome the economic crisis is to grant decision-making powers to workers' councils.

The party's ideas for economic reform may be clarified at a Central Committee meeting Wednesday which has been called to discuss self-management. While accepting the idea in theory, in practice most party leaders still want to retain a much larger measure of control over economic decision making.

In the official Communist view, economic power and political power are largely synonymous. Walesa's claim that the present phase of confrontation between Solidarity and the government does not involve issues of power is therefore unlikely to impress most communist officials.

Another speaker on the Solidarity television panel, Leszek Waliszewski, struck a different tone from Walesa when he said: "I want to see power taken over by the working people of the cities and the countryside, as is written in our constitution."

Assessing the results of the first year of Solidarity's existence, Walesa said much had been won on paper, but little in material terms.

"Thousands of agreements have been signed but there is nothing in the shops and life is becoming worse. We are not seeking confrontation, we want to master the unrest and come forward with constructive proposals," he said.

Another Solidarity leader, Ladislaw Frasyniuk, said the union's biggest success was that it managed to operate within a system of "totalitarian power" and, despite everything, had not been subordinated to that power.

The Associated Press reported the following: The official PAP news agency distributed an interview Walesa gave to a Roman Catholic newspaper in which he said, "Things have now reached a stage when the authorities are losing social acceptance and social support. This situation forces us to take upon ourselves responsibility for the fate of the nation."

In the interview, first published yesterday in the Catholic daily Slowo Powszechne, Walesa said he often feared for the union's future.

"In my opinion, the greatest success of Solidarity is that it survived this year," he said, referring to the time since the signing of the Gdansk accords permitting the creation of the independent trade union on Aug. 31, 1980.

The leaders of the independent farmers' union Rural Solidarity said at a news conference today they would ask their 1.7 million members to withhold tax payments to protest some government farm policies.