Brasilia, March 7 (IANS/EFE): Brazil's Supreme Court has authorised the investigation of the heads of two houses of Congress and 45 other politicians for their involvement in oil giant Petrobras scandal.

Petrobras, which represents 12 percent of Brazilian GDP, is currently under investigation following disclosure of widespread corruption said to have cost the company billions of dollars since the mid-1990s.

The scandal involves accusations that some of Brazil's leading engineering and construction companies formed a cartel to overcharge for Petrobras contracts.

The companies then allegedly split the extra money with corrupt Petrobras officials while setting aside some of the loot to pay off politicians who provided cover for the graft.

The top court on late Friday gave prosecutors authorisation to probe dozens of politicians, the vast majority of them from parties that are part of the ruling coalition, over the kickback scheme.

The biggest names on the list are the president of the Senate, Renan Calheiros, and the speaker of the lower house, Eduardo Cunha.

The scandal has led to the resignation of top company executives, including Maria das Gracas Silva Foster, who was replaced as Petrobras' CEO by Aldemir Bendine, former chief executive of state-run bank Banco do Brasil.