Polish workers scored another major political victory on the ruling Communist Party Politburo. One of the seats went to a member of the independent trade union federation Solidarity.

The elections to the Politburo and Secretariat, traditionally the founts of power in a communist country, came on the next to last day of the special party congress that has changed the face of Polish politics.

Once virtually excluded from any influence in decision-making, the party's rank and file now apparently will have a major say in the way the country is run.

The new 15-member Politburo elected at a Central Committee meeting today contains only four of the former members. One of these is Stanislaw Kania, who was elected party leader yesterday in the Soviet Bloc's first openly contested election for a country's highest leadership position.

Among the 11 newcomers is the first woman to be elected to the ruling body. She is Zofia Grzyb, 53, a foreman at a shoe factory in the central town of Radom and a member of Solidarity.

Political analysts said the Politburo appeared slightly more reformist than its predecessor, which contained several outspoken conservatives. Nevertheless, Kania, who drew up the list of candidates, has managed to retain much of the old political balance by his allocation of jobs in the powerful Secretariat.

One of the key posts on the seven-member Secretariat goes to Gen. Miroslaw Milewski, the former interior minister, who has been given overall responsibility for administrative and security affairs, including the Army and police. His appointment -- he was also elected a member of the Politburo -- was seen partly as an attempt to reassure the Kremlin that its interests are being well looked after by the new leadership despite the big changeover.

Milewski is regarded as a hardliner, and he has made several tough speeches calling for stronger action against Solidarity.

Polish newspapers predicted that the new leadership would not enjoy much of a honeymoon. The first major test will come next week when several strikes are planned around the country over issues ranging from workers' demands to appoint their own director to the increasing shortages of food.

In an address to the congress, Premier Wojciech Jaruzelski warned that the government would be forced to "decisively fulfill its constitutional obligations" should the need arise to save the nation from catastrophe and the state from disintegration. This was seen as a threat to introduce emergency measures unless new conflicts are solved through negotiation.

Jaruzekski painted a grim picture of the economy, predicting that national income would drop by 15 percent this year, that the money supply would rise by 23 percent, and that the supply of goods to the market would decrease by 10 percent. He said Poland's foreign debt, which is calculated by Western economists at between $26 billion and $27 billion, would increase by a further $3 billion.

In such a situation, he said, it would be impossible to grant pay increases to any groups of workers. He added that the government would press ahead with major economic reforms based on the independence of individual factories and more efficient central planning. Price increases averaging 110 percent will be necessary to restore the balance on the market, he said.

In addition to Kania, Politburo members reelected today include his rival for the post of first secretary, Kazimierz Barcikowski, Jaruzelski and Stefan Olszowski. In the Secretariat, Barcikowski has retained responsibility for party affairs and Olszowski remains in charge of ideology and the mass media.

The remaining key jobs in the Secretariat, responsibility for foreign affairs and the economy, go to two newcomers, Jozef Czyrek and Marian Wozniak. Czyrek is a professional diplomat who became foreign minister and Wozniak is one of the new regional party chiefs.

In addition to the four survivors, members of the new Politburo are two former Cabinet ministers (Milewski and Czyrek), four workers (Grzyb, Jan Labecki, Albin Siwak, and Jerzy Romanik), two academics (Hieronik Kubiak and Zbigniew Messner), and three regional party secretaries (Stanislaw Opalko, Tadeusz Porebski, and Tadeusz Czechowicz).

Labecki, 38, the youngest member of the Politburo, is a welder and party secretary in the Lenin Shipyard in Gdansk, the scene of last year's massive strikes in which he took part. A member of the outgoing Central Committee, he gained a reputation as a reformer because of his calls for sweeping changes in the party's power structure.

Balancing him is Siwak, a construction foreman at the Warsaw steel mill, who has won a reputation as an outspoken opponent of Solidarity. He once accused Solidarity leader Lech Walesa of being a paid agent for a Western intelligence agency.

About Kania, he once said: "I praise you highly for solving conflicts without resort to force, but I rebuke you for the fact that here is no law in our country."