A legislator investigating government corruption said Friday that Brazil's postal service and at least three private companies may have provided kickbacks to the governing Workers' Party (search).

The corruption scandal, which emerged in June, has paralyzed the government and forced the resignation of legislators and top aides of President Luiz Inacio Lula da Silva (search).

So far Silva, Brazil's first elected president, has not been directly linked to the scandal, but his popularity has fallen sharply and it is unclear whether he will run for re-election in 2006.

Rep. Gustavo Fruet told the government news agency Radiobras (search) at least three private companies and the post office may have provided funds for illegal campaign financing and for bribing allied lawmakers to vote with the governing coalition in Congress.

Fruet said the private companies would be named when his commission issues a report on Wednesday.

Rep. Osmar Serraglio, head of the congressional probe, said Thursday the DNA advertising agency had received a $26 million advertising contract from the government-run Banco do Brasil and funneled $4.5 million of it back to the Workers' Party. The owner of the DNA advertising agency has denied the charges.

The corruption allegations surfaced when former Rep. Roberto Jefferson accused the Workers' Party of paying monthly bribes to lawmakers in exchange for their support in Congress.

Party officials were forced to resign, and Jefferson later was impeached for his role in the scandal.