MONTREAL—As his testimony painted an increasingly clear picture that engineering firm Dessau profited handsomely from corrupting Quebec’s institutions, the anger directed at Rosaire Sauriol came from all sides.

Over three days of testimony at the Charbonneau Commission, Sauriol openly admitted to raising millions in illicit contributions for political parties for a system of corruption that spread far beyond Montreal. On Thursday, he admitted to claiming tax deductions for his efforts.

“You corrupted people and you demanded tax credits?” asked an incredulous commissioner. “If you say so,” answered the engineering vice-president.

The tone of the answer triggered angrier exchanges, leading to another outburst from a city lawyer.

“Isn't it disgusting what you did?” he asked. “You can use that language if you want,” shrugged Sauriol.

After days of pointed questions, Sauriol continued to deflect blame. He triggered looks of disbelief when asked if Dessau ever landed contracts in corrupt third-world countries, bypassing Canadian law.

“We refuse to work in countries like that and that's the way it is.”

Outraged commissioners wondered if the prospect of facing fines or even jail for breaking the law was ever a source of concerns. Sauriol answered that his fears were not the legal kind.

“Consequences were a lot worse for the; reputation of the company,” said Sauriol. “The sentence is something, but the reputation is something else.”

Sauriol admitted to creating $2 million worth of false bills to generate cash for political contributions, while employees were refunded for whatever amount they gave.

“You corrupt the world and it is tax deductible,” said City of Montreal lawyer Philippe Berthelet.

Sauriol also offered a gift of $5,000 to the former head of Union Montreal party funding, Bernard Trépanier, for his 70th birthday.

Dessau Engineering eventually dropped all their collusion and corruption efforts. In 2009 they even notified the tax department, to report their illegal cash transactions. Justice Charbonneau didn’t believe in the goodwill of the gesture.

“It's your fear of getting caught that incited you to change and go 90 degrees?” asked Charbonneau. “No, we just decided to review; our set of values and do what was right,” Sauriol answered.

Sauriol's testimony is over for the time being, but he's expected to come back to talk about corruption in Laval.

—with files from The Canadian Press.