MONTREAL -- A construction boss who pinned the blame for collusion on a mid-level Montreal municipal functionary is having his credibility shredded at Quebec's public inquiry.

Joe Borsellino, head of Garnier Construction, has been forced to explain inconsistencies and major memory gaps in his testimony.

For instance, on Wednesday morning, he couldn't recall having deposited $1.8 million at the bank in 2004. On Wednesday afternoon, he admitted to making the deposit and blamed inquiry lawyers for the way the question was phrased.

Under intense questioning, he also suggested the Mafia might play a role in Quebec's construction industry and he said he personally knew members of the Rizzuto crime family.

But he wasn't too sure about the specifics.

When asked about personal relationships, he blamed a 2009 beating he received -- Borsellino called it an "accident" -- for having caused memory problems.

He said he couldn't recall whether or not he had been invited to a Rizzuto family wedding. As for the Mob's role in the construction industry, he described it as "rumours" he didn't explore.

Borsellino's testimony was a cacophonous medley of incomplete, contradictory answers as inquiry lawyers sought to poke holes in his claims of the previous day.

He had laid blame for Montreal's crooked construction industry at the feet of Gilles Surprenant -- a mid-level municipal bureaucrat.

On Wednesday, Borsellino conceded that a Montreal contract he lost had been rigged, although the man he accused of creating the crooked system, Surprenant, had nothing to do with the contract.

The businessman said he gave both Surprenant and another city official, Luc Leclerc, about $100,000 each over the years, while giving other city employees other gifts like hockey tickets and bottles of wine.

Both bureaucrats have admitted to taking bribes -- but with the exception of Borsellino's testimony, neither has been described as a mastermind of the collusion system.

Borsellino was also questioned Wednesday about his motivations for taking Montreal's former public works director to Italy in 2008.

Borsellino had claimed that he took Robert Marcil to Italy to develop a business relationship following a series of cancelled contracts.

But inquiry counsel attempted to pick apart that claim that relations with the city were poor and needed some repairing. Inquiry lawyer Simon Tremblay found a number of other reasons for the contracts being cancelled.

In one case, a contract cited by Borsellino was actually not even located in the City of Montreal.

Tremblay suggested Marcil was actually invited to Italy as a thank you for signing off on a $5.5 million contract that Garnier won in 2007 for emergency sewer work without any bids.

He flatly declared that he didn't believe Borsellino's explanation for the Italy trip.

"We know it's not true," lawyer Simon Tremblay snapped at one point, expressing disbelief at Borsellino's description of his relationship with the city.

Tremblay told Borsellino that a police wiretap picked up a conversation at the airport between Borsellino and Jocelyn Dupuis, a union boss, before they departed for Italy.

Dupuis is overheard asking for Marcil's name because he had never met him before, Tremblay said.

"You told him he is the director of public works and he gave you a contract for $5.5 million last year," Tremblay added.

Confronted with an alleged cash deposit in October 2004 of $1.824 million at a certain bank branch, Borsellino initially said he was unaware of such a transaction then revised his story.

Meanwhile, commission officials have not confirmed the next witness will be Nicolo Milioto, a construction boss who has been described at the inquiry as the intermediary between the Mafia, municipal politics and the construction world.

Milioto has been present the last two days with his lawyer.

Milioto was allegedly seen by police at Cafe Consenza, a known Sicilian Mafia hangout, 236 times over two years.

Video surveillance showed him handing stacks of cash to the since-murdered Mafia don, Nicolo Rizzuto, who would promptly stuff the cash into his socks.

Police said they'd never heard of Milioto before, but later identified him as a key "middleman" between the construction industry and the Rizzuto clan.