Recently-seized documents show that former Polish president and Solidarity founder Lech Walesa was a paid informant for the communist-era secret security between 1970 and 1976.

Mr 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.

Lukasz Kaminski, head of the state National Remembrance Institute, said on Thursday documents seized from the house of the last communist interior minister, the late General Czeslaw Kiszczak, include a commitment to provide information to the secret security that is signed with Mr Walesa's name and a codename, Bolek.

There are also pages of reports and receipts for money signed by Mr Walesa.

The 279 pages of documents will be made public in due course, Mr Kaminski added. He said historians need time to analyse the content of the documents.

Mr Walesa, 72, speaking from Venezuela where he is travelling, suggested the papers are fake.

"There can exist no documents coming from me. I will prove that in court," he said.

Communism and Moscow's control were imposed on Poland and other countries in the region after the Second World War and were despised and opposed by most people.

Secret security was the regime's harsh tool for keeping the people under control, using personal information to blackmail and discredit critics.

The secret service also used to fabricate information on people, a fact that calls for meticulous confirmation of any compromising documents that emerge.

Mr Walesa was the icon of Poland's and eastern Europe's drive for freedom that abolished communism and brought down the Iron Curtain in 1989 without bloodshed.

He founded and led Solidarity from 1980, when it was formed out of worker protests, and he was Poland's president from 1990 to 1995.