Three aides of Luiz Inacio Lula da Silva, Brazil's former president, have been convicted of fraud in relation to a vote-buying scheme in Congress.

A court spokesman said former chief of staff Jose Dirceu was found guilty by six of the 10 judges in connection with the scheme that ran from 2002 to 2005 during Lula's first term.

Jose Genoino, the head of Lula's ruling Workers' Party (PT) at the time, as well as its treasurer, Delubio Soares, were also convicted on charges of corruption.

The men are just three among a total of 37 former ministers, politicians, businessmen and bankers on trial before the Supreme Court over the scandal known as "Mensalao", or "big monthly payments".

Up to 30 of the defendants have already been found guilty, since the trial began in early August.

The justices said Dirceu, Genoino and Soares distributed money to politicians to "illegally secure the support of other political parties to form a ruling government coalition".

The defence argued that the illegal account was used only to cover campaign costs for buying political support in Congress - which is a common practice in Brazil.

Dirceu served as Lula's de facto prime minister and is viewed as the main culprit in the high-profile trial which threatens to tarnish the former president's legacy.

The scandal nearly cost Lula his re-election in 2006. After winning the election, at the end of his second four-year term, Lula went on to hand power to his protégé and fellow PT member Dilma Rousseff.