"There can be no materials on my undertakings. If there were any, there would have been no need to counterfeit them," Walesa wrote on a Polish microblog.
Lukasz Kaminski, the head of the National Remembrance Institute (IPN), a state body responsible for researching Soviet-era crimes, told reporters earlier in the day that a batch of recently-discovered documents proved that the 72-year-old was an informer for secret services of that time.
Walesa was assigned the codename "Bolek" and was paid for his services to the country’s Communist authorities, according to IPN. Later, he actively campaigned against the regime and served as president of the Polish state from 1990 to 1995.
The documents were reportedly seized on Tuesday from the widow of former interior minister Czeslaw Kiszczak, who wanted to sell the papers to IPN. Prosecutors retrieved them the same day due to a law on important historic documents.