Warsaw - Polish Prime Minister Donald Tusk's party suffered another blow Monday with the launch of an investigation into alleged wrongdoing during the auction of historic shipyards in Gdynia and Szczecin, famous for their anti-Communist protests in the 1980s.

The investigation by prosecutors, reported by local media, threatens to further tarnish Tusk's Civic Platform a year before presidential elections. It comes after the resignation last week of three government ministers in a gambling lobby scandal.

Tusk is expected to challenge President Lech Kaczynski for the country's top post.

Prosecutors are to investigate officials at the Industrial Development Agency and the Ministry of Treasury suspected of "hindering the auction" of the two shipyards, Polish media reported.

The investigation follows a report in a local weekly that alleged officials involved in the auction process had favoured Stichting Particulier Fonds Greenrights, an entity reportedly backed by investors from Qatar.

The Gdynia and Szczecin shipyards remain unsold after Particulier Fonds Greenrights missed an August deadline to transfer funds to finalize the purchase.

The yards are known for the protests held there in the 1980s. Later strikes in nearby Gdansk resulted in the formation of the Solidarity labour union, which helped bring down the Communist regime.

The yards ran into financial hardship after the fall of Communism in 1989 and were kept afloat by state aid and production guarantees.

Poland is attempting to sell the yards' assets and use the proceeds to repay creditors and return aid that the European Union considers illegal. (dpa)