It was revenge time Monday at the Charbonneau Commission as a former union executive was cross-examined after revealing union secrets in his testimony three weeks ago.

Whistleblower and star witness Ken Pereira didn’t lose any of his fight three weeks after suffering a head injury in a fall one morning as he left his home to testify at the corruption inquiry.

A lawyer representing the Provincial Council of Construction Trades attacked Pereira’s work ethic when he began as a union rep.

Pereira wasn’t pleased with the accusations.

"I am telling you there is discrimination in our industry and it's done by both sides, including yours. If you are trying to discredit me on minor details, that's fine. I can release 84 hours of recordings of workers talking to contractors who say that I have the okay from all the contractors who tell me 'Ken, there is discrimination,'" said Pereira.

Exchanges became testier when FTQ-Construction lawyer Serge Turcotte suggested Pereira was a thief for removing incriminating documents from the FTQ’s accounting office.

The aggressive line of questioning saw Pereira fight back.

“If he wants to spit at the witness, as the saying goes, then let's draw the line somewhere,” he said, leading Justice France Charbonneau to intervene in Pereira’s defence.

“Even if you managed to prove that Pereira is a pit bull, what would be the point anyway?” she said.

Pereira still managed to lose his temper, telling Turcotte, “(Union leader) Jocelyn Dupuis was not a colleague. If there's a commission, it's because of guys like him,” when Turcotte claimed Pereira was simply after Dupuis’s job as head of FTQ-Construction.

Charbonneau issued a warning, refusing to hear that line of questioning.

During his testimony, Pereira said that he had been recruited by the Quebec Federation of Labour in an attempt to convince construction workers to switch unions, and soon afterward discovered immense corruption within the union.

He said that members of the Hells Angels and the Mafia were determining which union members were getting union permission to work on job sites, and that they were influencing loans given by the QFL's investment arm, the Fonds de Solidarité.

The commission is set to introduce wiretap evidence involving the FTQ-Construction leader later this week.

The Charbonneau Commission resumes Tuesday.