Speaking on the radio station RMF FM, the former Solidarity leader said that it would be a "disaster" for Poland if Jaroslaw Kaczynski, the identical twin of Lech Kaczynski, the Polish president killed in an April plane crash, won.

"Kaczynski is an irresponsible and dangerous politician," said Mr Walesa. "We could pay a high price if he wins."

Mr Walesa's attack came just hours after Mr Kaczynski won 36.7 per cent of the vote in the first round of Poland's presidential elections. He came just 5 per cent behind Bronislaw Komorowski, his main rival for the post.

With neither candidate securing an absolute majority, the two will face each other in a run-off vote on July 4.