Lech Walesa, the former shipyard worker who helped bring about the collapse of communism in Poland and then served as its president, faces new accusations that he was an informant for the secret police during the Communist era.

For many years, accusations of collaboration have dogged Mr. Walesa, the leader of the Solidarity movement, who won the Nobel Peace Prize in 1983 and served as president from 1990 to 1995. A special court cleared him in 2000.

But he faces new allegations from a trove of documents that prosecutors confiscated on Tuesday from the home of the widow of Gen. Czeslaw Kiszczak, who as interior minister helped crush Solidarity in 1981, when martial law was imposed, and was briefly, in 1989, the country’s final prime minister under the Communist regime.

The documents include 350 pages of secret-police files that have never been open to public view. They mention a man called Bolek, which is said to have been Mr. Walesa’s code name, according to Lukasz Kaminski, the head of the Institute of National Remembrance, a government-run commission established in 1998 to investigate crimes committed during the Nazi occupation and Soviet domination.