An agreement to end a strike in Poland's major shipyards collapsed early today when walkouts spread along the Baltic coast and strikers called for sweeping political reforms as their price for going back to work.

The presentation of the new demands, following the collapse of a tentative agreement to end a strike at the giant Lenin Shipyard in Gdansk, added a serious new dimension to Poland's gravest crisis in 10 years.

The demands were formulated by an integrated strike committee which claims to be empowered to negotiate on behalf of workers in 24 factories in the Baltic seaports of Gdansk, Gdynia and Sopot. The 16-point list of grievances goes to the heart of the communist system under which Poland has been ruled for 35 years.

Among the political demands are legalization of the right to strike, abolition of censorship, release of all political prisoners, full public discussion of new economic policies, access for the Catholic church to news media, and the end of Communist Party interference in the work of trade unions.

The economic demands include a monthly increase of 2,000 zlotys ($68 at official rate) for all workers, abolition of privileges enjoyed by Communist Party officials, improved food supplies, inflation-linked wages, and abolition of special shops where purchases can be made only in hard currency.

It is clear that the workers themselves are more interested in improving their living conditions than large-scale political reforms. But representatives of Poland's active dissident community are becoming increasingly influential at strike meetings and in the formulation of worker's grievances.

[Dissidents said that one of their prominent leaders, Jan Litynski, was placed under house arrest Sunday night, news services reported. The chief spokesman for the dissident Self-Defense Committee was accosted by police when he left his apartment during the day and told to remain at home for the time being, according to the sources.]

Official hopes for an early end to the strikes were shattered last night when workers at the Lenin Shipyard overruled a decision by their own strike committee to return to work. With 16,000 workers, the Lenin yard was the first plant in the Baltic region to strike, on Thursday, and has set the pace for subsequent negotiations.

Fearing isolation, workers in other plants asked the shipyard strikers to continue their three-day occupation as a gesture of solidarity. This was followed by the formation of the integrated strike committee, which workers hope will form the basis to a new independent trade union movement after the strikes are over.

According to latest reports from Gdansk, no significant negotiations with managements took place today. Meeting in the Lenin yard, committee leaders argued among themselves over tactics and waited to meet government representatives.

Visitors to the Gdansk shipyard today reported that the leaders may have problems keeping their followers united since, after four days sleeping at the yard, many workers are tired and dirty. Much depends on what happens Monday when work was meant to resume under the collapsed agreement.

A priest offered an open-air mass before some 3,000 workers and their families inside the gates of the Lenin Shipyard, Agence France-Presse reported from Gdansk. The site was where shipyard workers were killed in bloody riots 10 years ago.

[The main gate was draped with the flags of Poland, the Vatican and the Virgin Mary, with a portrait of the Polish pope, John Paul II, facing the decks. AFP also reported workers' masses in Gdynia, which are said to have received official authorization.]

Meanwhile, the unrest triggered by a rise in meat prices on July 1 continued more sporadically in other parts of Poland. In the countryside south of Warsaw, a meeting of peasants agreed to strike Monday in solidarity with the Gdansk workers.

The peasants are to refuse to sell their products to government purchasing agencies. The peasants called for a meeting with representatives of the Ministry of Agriculture.

The Communist Part chief in the Gdansk region, Tadeusz Fiszbach, is reported to have guaranteed strikers security until Monday morning. This leaves open the question of what happens then. So far there has been no suggestion that the government intends to revise its policy of avoiding force.

Communist Part chief Edward Gierek is due to pay an official visit to West Germany on Tuesday and would not want such an important event to be marred by riots at home.

The inside story of how the talks at the Lenin Shipyard broke down illustrates the worker's enormous mistrust of the communist leadership and their memories of the December 1970 riots in Gdansk, when at least 55 people were shot dead.

Gierek has adopted a much more conciliatory approach than that of his predecessor, Wladyslaw Gomulka, who was toppled in 1970. But Gierek seems incapable of stopping the strikes from spreading.

By Friday evening, it seemed as if differences were rapidly narrowing between the two sides at the Lenin yard. The next day, both management and a strike committee had agreed to a pay rise of 1,500 zlotys ($45 a month) for all workers. There were also writen guarantees of security for the strikers and pledges to reinstate workers dismissed because they advocated free trade uniforms.

Both officials and workers throughout the Gdansk region are well aware of the unique importance of the Lenin yard -- and the political power held by its strike committee. Around noon on Saturday, a delegation of Gdansk bus drivers had come to the yard after hearing that the strike was about to end.

The striking drivers were afraid that, without the Lenin Shipyard supporting them, their bargaining power would be much reduced. One driver remarked: "If you abandon us, we'll be lost because buses cannot face tanks."

The Lenin strike committee was itself split between those who wanted to settle their own dispute and those who favored maintaining solidarity with other plants. According to a vote taken at 3 p.m. on Saturday, the majority was in favor of a settlement.

The committee's decision was announced to the workers an hour later by the strike leader, Lech Walesa. His voice hoarse after three days of talking with little sleep, he told the workers they should accept the agreements.

This was greeted by shouts of "no" from some workers and a young woman yelled that Walesa had betrayed the strikers.

At this point, Walesa is reported by observers at the meeting to have abruptly changed course. He told the workers, "All the factories came out with us and therefore we must be with them. The fact that we've won doesn't mean that they've won. We must fight alongside them until the end."

The meeting then decided to continue the strike until the demands of workers elsewhere in the region had been met.

Walesa and other members of the strike committee then went to other plants in Gdansk to assure that the Lenin Shipyard would not abandon strikers elsewhere until demands were met.

While the leaders were away, events at the Lenin yard took a new twist. Someone came onto the loudspeaker used to relay negotiations with management to workers outside the conference hall. The speaker told the workers that the strike was over and everybody could now go home.

The result was confusion. Convinced that they had won a great victory, workers began leaving the yard until they met Walesa and the strike committee returning from their tour. Once again, Walesa -- who organized the strike from the start -- persuaded enough workers to continue the occupation.

Events of the past few days appear to have strengthened the solidarity of strikers in different plants. At some, for example the Shipyard of the Paris Commune in Gdynia with over 10,000 workers, Communist Party members have been excluded from membership on the strike committees. This is because it is feared they might still be bound by their acceptance of Communist Party discipline.

On the other hand, the tactics of the authorities have paid off to a certain extent in the Lenin Shipyard itself. The original 8,000 or so workers occupying the plant have been whittled down to a hard core of a few thousand.