Looking haggard and weak, a leader of Poland's suspended Solidarity trade union today confirmed that he and 13 other imprisoned Solidarity activists were entering the second week of a hunger strike in protest against martial law.

The news of the hunger strike at Bialoleka Prison in Warsaw was given by Jan Rulewski, the detained leader of Solidarity's Bydgoszcz chapter, during a dramatic court appearance here. He was released from internment briefly to answer charges of careless driving that resulted in the death of a pedestrian in this country town, 25 miles north of Warsaw, in March 1981.

The case was adjourned after a doctor testified that, because of the hunger strike, the 36-year-old union official was too weak to stand trial. Rulewski managed, however, to tell a courtroom packed with his supporters that he and his colleagues intended to continue with the protest as "long as we are able."

The trial soon turned into a verbal tussle between Rulewski, who had a reputation of being one of Solidarity's most radical leaders, and the judge. Leaning on the dock for support, Rulewski was constantly interrupted as he tried to answer questions on his health with a political tirade against martial law.

The occasion provided a rare insight into conditions at Bialoleka Prison, where most of Solidarity's senior officials and advisers, with the notable exception of union leader Lech Walesa, are being held. Wearing a pin of red and white, the Polish national colors, Rulewski said that the hunger strikers had been denied regular exercise periods, tobacco and visits by relatives since the start of their protest.

Rulewski, who had grown a beard during his five months in captivity, said that the internees wanted to demonstrate their support for compromise proposals drawn up by the Roman Catholic Church for talks between Solidarity and the government. The church document calls for an amnesty for all political prisoners but also accepts that the union should bear some responsibility for the rising social tensions in Poland prior to martial law.

The church proposals have been rejected by the government as a basis for negotiations.

In addition to Rulewski, some of Solidarity's best-known officials are believed to be taking part in the hunger strike, which began on May 13 to mark five months of martial law. The protesters include the union's former deputy leader, Andrzej Gwiazda; its former press spokesman, Janusz Onyszkiewicz, and two senior advisers, Karol Modzelewski and Jacek Kuron.

Kuron, the founder of the dissident Committee for Social Self-Defense (KOR), is believed to share a cell in Bialoleka's block number four with Rulewski. It is in this block, which is isolated from the rest of the prison, that Solidarity's senior officials are kept.

A Solidarity bulletin earlier gave the names of 17 internees who would be participating in the protest, but Rulewski today referred to "the hunger strike of the 14." This suggested that three protesters had dropped out.

Pressed by the judge to describe how he was feeling, Rulewski replied, "I feel worse today than I did yesterday--and worse yesterday than a week ago."

There was laughter from spectators when he added that his condition had not been helped by the fact that he had been brought to the court in "neither a Chaika or a Lada Soviet-built limousines but a bitch"--the slang for a police van. He then indicated that the internees were well informed about the spate of street demonstrations and strikes that flared in many Polish cities earlier this month.

He said, "In the light of the determined resistance to martial law in the country, we decided to undertake our hunger strike for as long as we are able."

A doctor who examined Rulewski during a break said he had lost weight and was very excitable. His facial features had sharpened, his skin had yellowed, and his pulse and blood pressure were well above normal, according to the doctor.

The judge accepted the doctor's suggestion that Rulewski should be examined by specialists at Bialoleka before standing trial. She refused him permission to talk with members of his family on the grounds that he was still interned.