A former Petrobras executive told a congressional hearing in Brazil on Tuesday that the ruling political party received up to $200m skimmed from contracts with the state-run oil company, reiterating claims made in plea bargain testimony.

Pedro Barusco, a former executive at Petrobras’s services division, said he had received payments as early as 1997 and in larger amounts starting in 2004. He said the Workers’ Party treasurer, João Vaccari, and Renato Duque, who previously ran the services unit, also benefited.

Barusco estimated Vaccari, treasurer for President Dilma Rousseff’s political party, had received $150m-$200m between 2003 and 2014, based on the percentages of contracts he himself had received.

“I got a piece; they got a piece,” Barusco said. He has pledged to return $97m to public coffers as part of a deal he reached with prosecutors.

Barusco spoke at a time of escalating fallout from the scandal at Petroleo Brasileiro SA, as Petrobras is formally known, with dozens of lawmakers now implicated.

Barusco said he did not know who ultimately ran the scheme and to his knowledge the former Petrobras CEO Maria das Graças Silva Foster, who resigned along with other senior Petrobras management last month, was not involved.

Prosecutors started questioning Vaccari on 5 February but he has not been charged with any crime. His lawyer and the Workers’ Party leadership say the party receives only legal donations. Duque was briefly jailed last year and does not face criminal charges.

Forty people, including two other former Petrobras executives, have been charged in the southern city of Curitiba and 14 are currently in jail awaiting sentencing.

Many of those accused lead the country’s top engineering firms and are charged with forming a cartel that funnelled funds from Petrobras contracts to themselves and politicians.

Barusco said he first remembered seeing the cartel active on contracts to build the Abreu e Lima and Comperj refineries. Petrobras shares fell 4% on Tuesday.

Defence lawyers told Reuters this week they expect to see the first verdicts on some cases in Curitiba in about a month, possibly before all witnesses are heard, as the focus of the case moves to the politicians being tried by the supreme court.

Rousseff, who was chairwoman of the company’s board when much of the graft took place, has denied any knowledge of corruption at Petrobras and urged a thorough investigation.