A star witness at Quebec's corruption inquiry wrapped up his main testimony with some advice on how to clean up the industry.

Former construction boss Lino Zambito, who has admitted to taking part in bid-rigging and collusion himself, said companies or businessmen found to be involved in fraud or bid-rigging should have their licences removed for good.

Zambito said Tuesday there are loopholes that allow businessmen to get back into the industry by starting or buying other companies.

He said municipalities and the province could help eliminate collusion by hiring more of their own engineers and doing work internally instead of relying so heavily on private firms.

Municipalities must also do a better job of vetting contracts and look deeper into the backgrounds of those who win contracts, Zambito suggested.

The co-owner and vice-president of now-bankrupt Infrabec Construction was on the stand at Quebec's Charbonneau commission for a seventh day. His previous testimony has created a firestorm in Quebec, where his allegations of bid-rigging, collusion, illegal political financing and the intrusion of organized crime have made waves.

Challenged by lawyer

Inquiry lawyers completed their questioning of Zambito on Tuesday, then other lawyers began cross-examining him.

A lawyer for the City of Montreal challenged the 43-year-old to provide details to back up his claims about widespread corruption in municpial contracting. For instance, Zambito was asked who told him that he would need to pay a three per cent kickback from contracts to the Montreal mayor's political party — something Zambito has said he had to do.

He replied that he remembered being informed about the new policy at a meeting with other construction companies but could not recall who had actually informed him.

He was also asked how he knew for sure that the person he gave the money to actually turned it over to Mayor Gérald Tremblay's party. Zambito replied that he trusted that the man collecting the money, Mafia middle-man Nicolo Milioto, was telling the truth.

The city lawyer suggested that Zambito's testimony appeared based on hearsay. In an exchange with the witness, he quipped: "You were the man who saw the man who saw a bear?"

Further cross-examination in the days to come will delve into Zambito's other explosive allegations, including that construction companies colluded to drive up the cost of contracts; paid a 2.5 per cent commission to the Sicilian Mafia; bribed local officials and the mayor of Laval; and illegally funded political parties at the provincial level.