Mr Claes and two other former ministers were found guilty after a bitterly fought, four-month hearing seen by many as an indictment of the Belgian political establishment.
The three-year suspended jail sentence was handed down by the country's most senior court in Brussels, which convicted Mr Claes of corrupt dealings in two defence contracts awarded when he was economics minister in the late Eighties.
The court also gave two-year suspended sentences to former defence minister Guy Coeme and the former head of the French-speaking wing of the Belgian Socialist Party (PS), Guy Spitaels. The same sentence was meted out to Serge Dassault, head of France's Dassault aviation company, which was at the heart of one set of bribery accusations. He and Mr Claes were each fined 60,000 Belgian francs (pounds 1,070). Eight other former aides and associates were convicted and received suspended sentences of up to two years.
Although Mr Claes did not benefit personally, the court ruled that he must have known donations to his party were linked to the contracts. It concluded that, in 1988, Mr Claes had to know that when the Italian company Agusta SpA bid for a contract for 46 army helicopters, it was discussing a bribe for the Flemish-speaking Belgian Socialist Party (SP). The presiding judge ruled that, in the Agusta case, "the accusation of passive corruption has been proven for Willy Claes".
He said Mr Claes and others bent the contract rules at the expense of the rival bidder, France's Aerospatiale SA. The court also found that a donation of Bfr60m (pounds 1.07m) from Dassault Aviation SA was linked to an aircraft equipment deal.
The Agusta and Dassault bribes were paid to Belgium's Flemish-speaking and French-speaking socialist parties through secret Swiss and Luxembourg bank accounts. In 1989 Belgium outlawed such corporate donations to political parties.
The trial in the 15-judge high court came after the parliamentary immunity of Mr Claes and others had been been lifted. Prosecutors had to prove only that the Agusta and Dassault "gifts" were timed so closely to the awarding of contracts that Mr Claes and the others knew they were bribes.
Despite the length of the Agusta-Dassault hearing, it produced little new evidence. It opened in September amid a dispute about whether the huge body of evidence should be translated into Dutch as well as French. The origin of the hearing lies in the murder in 1991 of Andre Cools, a former socialist minister assumed to have known of the financial wrongdoing.
Mr Spitaels commented: "Of course we received money from companies, but there was never an act of corruption. This truth I will defend until my last breath, if only for the honour of children and grandchildren."
Mr Claes became Nato secretary-general in September 1994 but resigned when the investigation into his role in the Agusta case became increasingly intense. For Mr Coeme, a francophone Socialist, this was the second corruption- related trial in two years.Reuse content