Federal NDP Leader Tom Mulcair says he was contacted by the provincial police anti-corruption squad in Quebec to discuss a suspected 17-year-old bribe offered to him.

Mulcair says he never reached out to the police himself because he had no proof a bribe was actually being offered at a 1994 meeting with the now-controversial ex-mayor of Laval, Que.

Mulcair, who back then was a political rookie seeking provincial office for the first time, said he never looked to see what was in an envelope offered by then-mayor Gilles Vaillancourt.

He said he refused the envelope, cut short the meeting, and kept his distance from the powerful mayor of the suburb north of Montreal.

"I never saw cash," Mulcair said during a session with reporters Tuesday.

"There was never a question of cash."

At that point it was "absolutely impossible" that coming forward would have resulted in criminal charges, said Mulcair, who is a lawyer.

Media have posted a statement given by Mulcair in July 2011 to police in which he says Vaillancourt repeatedly told him, "I'd like to help you," while holding up an envelope in his hand.

The statement reportedly quotes Mulcair as saying he discussed the meeting with fellow Liberal Vincent Auclair, to whom Vaillancourt also allegedly offered an envelope.

Mulcair said he was contacted in 2011 by the anti-corruption squad created by the province in the midst of numerous Quebec scandals.

"Once the investigation was started, I was contacted to see if I would help and I was happy to do so," he said Tuesday.

He said he had no trouble doing his job as a member of the provincial legislature and later a minister in the Charest provincial cabinet because he had refused the envelope.

But the Conservative government isn't satisfied with Mulcair's explanation.

"He's got some important questions to answer to Canadians about what he knew about this corruption, why he covered it up, why he actually lied about having been offered an envelope of cash and these are important things for Mr. Mulcair to come clean with about Canadians," said government House Leader Peter Van Loan.

He was referring to comments by Mulcair, during a 2010 news conference, that he had never been offered a cash envelope in Laval. He maintains that he never actually had proof he was being offered a cash envelope.

Vaillancourt now faces several corruption-related charges, including gangsterism. He is denying the criminal charges against him and has, in the past, also denied offering bribes to fellow politicians.

One of those alleged targets was Serge Menard, a former federal and provincial MP with the Bloc Quebecois and Parti Quebecois. Menard was allegedly offered $10,000 cash by the mayor in 1993.

Like Mulcair, he was a rookie provincial politician on the verge of winning his first election. And like Mulcair, he says he refused the money, then decided to remain publicly silent about the incident.

Menard, a lawyer, is quoted in a Montreal La Presse report saying that what happened two decades ago is not technically illegal -- because corruption laws apply to civil servants, ministers and legislators.

He told the newspaper that the relevant Criminal Code articles don't make any reference to exchanges that involve regular citizens running as candidates for office -- which is what he and Mulcair were at the time of Vaillancourt's alleged offer.

Events in Laval are now under the microscope at the Charbonneau commission. Police allege that the city administration was run like a criminal racket, hence the gangsterism charges against the ex-mayor.

At the Charbonneau inquiry, a retired engineer confirmed Tuesday that he collected about $2.7 million in kickbacks from participants in a system of collusion that was operating in Laval between 2003 and 2009.

Roger Desbois testified the funds were diverted to Vaillancourt's municipal party and that the mayor was aware of the scheme. He said he was recruited into the plan in 2002 by Claude Asselin, the city's former director-general.

Asselin, he said, had done the job before him.

The money came from contractors who obtained work on the city's sidewalks, aquaducts and paving. The kickbacks were for about two per cent of the value of the contract.

Desbois also worked as a fundraiser for Vaillancourt and said the mayor asked him who was a good contributor and who was not.