The head of Poland's official trade unions, facing a mass switch by members to new independent unions, promised "radical changes" today to foster democracy and autonomy in the old unions.

Meanwhile, in his first appearance on Polish national television since becoming Communist Party chief; Stanislaw Kania vowed never to let the conditions that triggered this summer's labor revolts happen again, blamed the crisis on the country's leadership and declared himself in favor of a special party congress to prepare a plan of action.

He asserted that Polish labor's principal demand -- freedom to form free trade unions -- "came from a lack of trust in the old unions."

Kania stressed close ties with the Soviet Union and appealed for understanding from the West. He also disclosed that he had spoken to Soviet President Leonid Brezhnev Saturday -- the day Kania was named to head the party -- and that Brezhnev had promised the Soviet Union's "full support" to get Poland out of its trouble.

[In Moscow Thursday night, the Soviet Union announced it would send extra food and manufactured goods to Poland in order to buffer the impact of the strikes, Washington Post correspondent Kevin Klose reported. Details on page A26.]

The Warsaw leadership's chief concern at this point is getting the country back to work. For despite the signing of the unprecedented agreements last month with the nation's most important industrial groups, sporadic strikes continue and, perhaps more damaging to the recovery effort, workers are taking time off to discuss local grievances and the idea of forming independent unions.

Although government officials have repeatedly affirmed their intention to let free unions form throughout the country, organizers of an independent trade union in Warsaw area -- including a broad base of factory and institute workers -- called a press conference today to complain of harassment. The Warsaw organizers reported rates of defection to their union at between 50 and 80 percent in different city plants.

Independent unions have no precedent in the communist East Bloc. Under the party system, they are not supposed to exist since, like everything else, unions are expected to be adjuncts of the party.

The creation of associations is forcing the old ones to defend workers' interests more competitively or risk being left with a top-heavy bureaucracy and very few members.

While, privately, Polish authorities are very alarmed by the trend, publicly they call for unity of the Polish worker movement and stand by the old organizations.

The television broadcast showed two speeches by Kania, in direct terms and a rather relaxed manner, to party ativists in Gdansk and Katowice earlier this week.

It amplified greatly and in parts differed considerably from versions paraphrased by announcers and printed in the Polish press Monday and Tuesday.

Poland's Central Council of Trade Unions, which overseas the official unions, began circulating handbills this week to its 40,000 affiliates, promising a "revival."

At a press conference today, Council Chairman Romuald Jankowski pledged changes in the official unions -- among them, new local elections will be allowed in any factory where workers are unhappy with their representatives.

In general, Jankowski said the old union movement would become more independent of the authorities -- language borrowed from the recent strike movement.

Three processes seem to be going on in Poland's churning union movement. First, committees are being set up to organize new free unions. Secondly, some official unions -- such as the seamen and dockwworkers' union and the union of workers of culture and art -- are leaving athe central trade union council but not disbanding. Thirdly, the central council is fighting for its existence and promising self-reform.

With Poland's labor scene still very much in flux, many questions about how the new union structure will ultimately work have been left dangling.

For instance: How will the large funds held by the old unions be shared, if at all, with the new ones? Now that workers have won the right to strike in Poland, where will the strike support come from? Will it be necessary to form a new central union council or some sort of federation?

The official labor paper, Glos Pracy, this week published a draft proposal for a trade union law revamping the Stalinist-era statue workers criticized as undemocratic and unrepresentative. The draft plan will be submitted to the Polish trade union congress in November and for final approval to parliament in December.

"Regardless of how the situation shapes up," Jankowski said, "we will not treat the new unions as hostile people."

The union chief called the division-of-funds question "a secondary problem."

He added, "The main thing is that the funds act toward the well being of workers."

Asked about reports of harrassment, Jankowski said, "You have to understand some things are being done by people who are wrong."

Admitting that the official unions committed "numerous faults" in the past. Jankowski said he expected the old council structure to survive. "I do not think there will be nothing for us to do. I think there will be enough for both [old and new] unions," he said.

One immense problem for the old unions is the 13,000 full-paid functionaries they carry on their payrolls if they have to trim their administrative ranks.

Jankowski defended past achievements of the Polish trade union movement, takng credit for improving working conditions and wages. He also rebutted the common view that the official unions are under the party's thumb. Janknowski is himself a deputy member of the central committee.

Meantime, Warsaw Radio reported strikes continuing today in the north-eastern part of the country, particularly in the large industrial area of Bialystok. But the broadcast said the work stoppages were on a reduced scale and involved mostly small enterprises and a few agricultural cooperatives.