Poland’s democracy champion and Solidarity founder Lech Walesa said Monday that signatures on documents that purport he was a communist-era paid informant aren’t his.

Walesa was speaking on TVN24 in his

first public appearance in Poland since photocopies of the documents were released by a state history institute last week.

“I never betrayed anyone. I was never an agent. I never took any money. Never,” Walesa said.

When the journalist interviewing him showed him images of the photocopies, Walesa said “I signed nothing. These aren’t my signatures. This is very nice handwriting. My handwriting is terrible.”

To stress his point, Walesa, a 72-year-old Catholic, made the sign of the cross.

He rejected calls by some critics that he confess and argued that the documents were fabricated.

“You can kill Walesa, but you cannot defeat him,” he said.

Earlier Monday, Walesa said he might sue the institute.

For years, he has been denying allegations that he informed on others to the communist security police in the 1970s. He insists that the documents released by the state National Remembrance Institute are forged. But he has also admitted in the past to having signed some documents for the communist-era security police in the 1970s and recently said he had made a “mistake,” but didn’t specify its nature.

In 2000, a special court cleared him of collaboration allegations, saying it found no proof.

Walesa said he wants to see the files held at the institute and that the issue will “probably” end up in court, where he will want to prove that they have been fabricated. The documents were recently seized from the home of a communist-era official and were speedily released by the institute without deeper examination by experts.

In 2011, the institute said that in the early 1980s communist authorities tried to prevent Walesa from getting a Nobel Peace Prize by fabricating documents to suggest that he was a collaborator. In spite of that, Walesa got the prize in 1983 for founding and leading Poland’s Solidarity freedom movement.

Also Monday, the institute’s prosecutors were searching the house of late communist-era leader General Wojciech Jaruzelski for any documents that could be found there. Jaruzelski imposed martial law in 1981 and had Walesa arrested, as he sought to crush Solidarity. The nationwide movement prevailed, leading to the 1989 ouster of the communists.