Poland has been forced to move its celebrations to mark the 20th anniversary of the country's first free elections away from the city regarded as the birthplace of the democracy movement in the Soviet bloc.

The government has announced it is moving events away from Gdansk because of a threat of violent protests from the Solidarity trade union.

Gdansk Shipyard was the birthplace of the Solidarity trade union movement, whose opposition to the Soviet regime led to the end of Communist Party rule in 1989.

But Donald Tusk, the Polish prime minister and an activist under Communism, has taken the decision to shift the commemoration of the June 4 vote to Kraków on the far side of the country.

He told the Daily Telegraph that Solidarity had put the safety of the event at risk by refusing to give a pledge of non-violence.