BRASILIA • Brazil's top prosecutor has requested that President Dilma Rousseff be investigated for trying to obstruct a sweeping corruption investigation involving state-run oil firm Petrobras, local media reported late on Tuesday.

An investigation could well mark the political end for the beleaguered leader of the world's seventh-largest economy as it would be the first time that Ms Rousseff would be directly implicated in Brazil's biggest-ever graft case.

She is already likely to be suspended from office as early as next week on unrelated charges of breaking budgetary laws.

The corruption scandal casts a shadow over 13 years of Workers Party rule that saw Brazil's middle class expand by some 40 million people since 2003 with the help of new social programmes.

Ms Rousseff has consistently maintained she has done no wrong, despite serving as the chairman of Petrobras' board for several years when much of a billion-dollar kickback scheme played out.

The case has already seen executives from Brazil's biggest construction firms convicted and jailed for siphoning funds from Petrobras to bribe politicians. Around 50 politicians are under investigation.

Prosecutor-General Rodrigo Janot's request will be analysed by Supreme Court Justice Teori Zavascki and is not public because it is based on recorded phone calls between Ms Rousseff and former president Luiz Inacio Lula da Silva.

Newspaper Estado de S. Paulo reported that Mr Janot had also charged Mr Lula with participating in a scheme to stop former Petrobras executive Nestor Cervero from collaborating with investigators. The federal prosecutors' office would not confirm the charge.

REUTERS