The former head of Montreal's public works department stuck to his story today during his testimony in front of the Quebec corruption inquiry, continuing to deny he was part of a system of corruption and collusion.

At the centre of today's questioning was Robert Marcil's role on the city's selection committees that choose engineering firms for public contracts.

Questioned repeatedly by the commission's lawyer, prosecution and commission chair France Charbonneau about his involvement on the committees, Marcil repeated over and over that he never accepted cash to rig bidding.

Marcil said the president of Génius Conseil Michel Lalonde, who was a previous witness at the Charbonneau commission, was lying when he said Marcil asked for money to rig a selection committee.

He accused Lalonde of trying to back at him for a job offer that he was refused.

The commission's lawyer drilled Marcil on why, as a high-level civil servant, he would serve on so many committees.

But Marcil said he was chosen to sit on the committees because of his expertise.

Yesterday the commission presented evidence that Marcil divulged detailed information about city bids and contracts to Giuseppe Borsellino, the head of Garnier Construction.

But Marcil said Borsellino asked for that information. He said it was a one-off incident and nothing out of the ordinary.

Today the commission continued to press Marcil about potential conflicts of interest.

But Marcil said he wasn't concerned about his relationship with people like former Union Montréal treasurer Bernard Trépanier and vice-president of Genivar, Yves Lortie.

He said he has been working in the municipal sector for years, and knows many people.

At one point, Charbonneau interjected, saying he would have to be an "imbecile" or "incompetent" to not see his relationships as a conflict while he was sat on selection committees.

Today was Marcil's third and final day of testimony before the commission.