Mounting allegations against a legislator from Australia's ruling party are threatening to bring down Prime Minister Julia Gillard's government, which enjoys only a one-seat majority in parliament.

Police say they are investigating whether parliament member Craig Thomson used a trade union credit card to pay for prostitutes while he was national secretary of the Health Services Union before entering parliament in 2007.

On Wednesday, current union officials said they have handed over to police additional information that has come to light in recent weeks. Union officials also disclosed that an independent probe requested by the union found suspected misuse of union funds while Thomson was its national secretary.

Thomson maintains his innocence. But if convicted and sentenced to more than one year in prison, he would be forced to leave parliament, depriving the government of its majority.

Ms. Gillard's party could still retain the seat in a by-election. But recent polls show her party's approval rating at an all-time low, making that highly unlikely.