The opposition True Path Party of former Prime Minister Tansu Ciller and the Islamist Virtue Party have both brought censure motions against Mr Yilmaz in parliament, accusing him of "abuse of power and secret links with mafia circles."

A key supporter of his minority government, Deniz Baykal, of the Republican People's Party (CHP), has backed the calls, putting the future of the administration in doubt.

The CHP holds the balance of power in Turkey's deeply divided parliament and, although it is not a member of the government, it has been supporting it on a case by case basis.

The allegations concern a businessman, Kormaz Yigit, who has said that figures at the highest level in government had helped him to buy a recently privatised state bank.

Organised crime

The businessman, who has denied having links with organised crime, has been questioned by police about the affair.

Two months ago a government minister who was a close confidante of Mr Yilmaz resigned from the cabinet and from parliament after a tape was released of his telephone conversation with Turkey's most notorious gangster.

A confidence vote in the Turkish parliament is expected in the coming few days.

Members of Mr Yilmaz's Motherland Party have rallied to his support and a party official described the charges against him as "unilateral accusations aimed at bringing down the government".

The prime minister has been meeting party officials and a statement is expected shortly.