In the testimony several months ago, Walesa denied that he wrote or signed recently found communist-era documents that suggest he was a paid informant for the communists in the 1970s. He said they were forged.
Critics of the new investigation, announced by prosecutors on Tuesday, contend that it is a new step by the governing Law and Justice party to diminish Walesa's status as leader and hero of the country's pro-democracy Solidarity movement of the 1980s.
Walesa insisted anew on Wednesday that he "never collaborated with any communist-era services, I was never on the communist side." He said the ruling party is "trying to carry out a political crime" against him, but will fail.
Law and Justice is led by Jaroslaw Kaczynski, who backed Walesa for the presidency in 1990 and worked in his presidential office, but then suddenly and bitterly fell out with him. Neither man has clearly explained the rift.
The current investigation was ordered by Justice Minister Zbigniew Ziobro, who is also the prosecutor general. A lawmaker for the opposition Modern party, Pawel Rabiej, said the ruling party was intentionally staining Walesa's reputation.
"I fault the current political team, which is trying to tarnish the authority of a person who is Poland's recognizable 'brand' around the world," Rabiej said. "I think this investigation is an instrument toward that goal."
But he also insisted Walesa has an "episode of collaboration with the (communist) secret police" in his biography and should "speak openly" about it. Law and Justice lawmaker Jan Mosinski said he trusts experts who said that Walesa's handwriting is on the documents. He added that the Solidarity leader's "legend" was "crumbling into rubble" because of his lack of frankness.