One of them said Belgian Deputy Prime Minister, Elio Di Rupo, had told them their legal costs would be paid, provided they said nothing against the French-speaking socialist party.

The revelations in the US$1m bribery case come just three days after the death of one of the main defendants from a heart attack.

Mr Claes is one of 12 accused facing corruption charges related to a defence contract.

Prosecutors say about $1m was passed from Italian helicopter-maker Agusta to the Flemish and French speaking socialist parties of Belgium.

Di Rupo denies any offer came through him

In return, Agusta won a contract to provide the Belgian Army with forty-six helicopters.

The Agusta affair, as it is known, has ensnared some of the country's most senior politicians in a scandal which has rumbled on throughout the 1990s.

The trial has been seen as a decisive opportunity to clean up Belgian politics.

But just as the case is due to go to court, three defendants are claiming the French speaking socialist party approached them offering to pay their costs on condition they did not attack the party during the trial.

The Deputy Prime Minister, Mr Di Rupo, has denied allegations any offer came through him.

The latest debacle follows the death on Saturday of the former head of Agusta who had been extradited from Brazil to stand trial.