The head of Poland's history institute says that recently seized documents show that former president and Solidarity founder Lech Walesa was a paid informant for the communist-era secret security from 1970-76.

Walesa has admitted signing a commitment to be an informant, but has insisted he never acted on it. In 2000 he was cleared by a special court.

Head of the state National Remembrance Institute, Lukasz Kaminski, said Thursday that documents seized this week from the house of the last communist interior minister, the late Gen. Czeslaw Kiszczak, include a commitment to provide information to the secret security that is signed with Walesa's name and codename, "Bolek." There are also pages of reports and receipts for money signed by Walesa.