The Brazilian attorney general's office said Wednesday it was extending the country's biggest-ever corruption probe, "Operation Car Wash," until January 31, granting the increasingly controversial investigation a new lease of life, for now.

Launched six years ago, the operation has put some of the biggest names in politics and business behind bars, including former president Luiz Inacio Lula da Silva.

But it has become increasingly bogged down by politics and controversy.

The mandate of the 14 prosecutors on the operation's task force in the southern city of Curitiba was set to expire Thursday, but the attorney general's office said in a statement it would renew it until January 31.

However, Deputy Attorney General Humberto Jacques de Medeiros rejected prosecutors' request for a year-long extension, citing budget shortfalls.

The operation has upended Brazilian politics and business since it was launched as a money-laundering probe.

Using an aggressive strategy of arrests and plea bargains, it has steadily pried the lid off a massive corruption scheme in which politicians and business executives plundered billions of dollars from state-run oil company Petrobras.

Suspects' tell-all confessions in exchange for lighter sentences sent tremors around Latin America, as it emerged that a laundry list of powerful politicians had taken huge bribes from one of the main players in the scheme, the construction company Odebrecht, in exchange for juicy public contracts.

The operation's success in bringing once untouchable figures to justice made it popular in corruption-weary Brazil.

But more recently, critics have accused the task force of pushing its aggressive tactics too far, provoking twin political and economic crises and undermining suspects' right to be presumed innocent until proven guilty.

It also faces accusations of playing politics, particularly after leaked communications appeared to show investigators conspiring to keep Lula, a leftist icon, from staging a come-back in Brazil's 2018 presidential race.

The operation will go ahead without its two most prominent figures, former judge Sergio Moro and lead prosecutor Deltan Dallagnol.

Dallagnol announced last week he was resigning for family reasons.

Moro left the judiciary to become justice minister under far-right President Jair Bolsonaro after the latter won the 2018 election.

However, he quit the government in April, accusing Bolsonaro of interfering in police investigations targeting the president's inner circle.