Boisbriand councillors Patrick Thiffault and Marlene Cordato say they were asked to not run for the mayor's office. (CBC)

Quebec's chief electoral officer has launched an investigation after a Quebec construction entrepreneur who handled several public works contracts was accused of trying to ensure the mayor in a suburban Montreal city could run unopposed in the coming election.

A report by CBC's French language service's investigative news program Enquête alleged that entrepreneur Lino Zambito colluded with Boisbriand Mayor Sylvie Saint-Jean to discourage her potential rivals from running in the city's Nov. 1 municipal election.

Details of the Enquête investigation were aired on Radio-Canada Thursday night.

"If someone asks a candidate to abstain from running by promising a donation … a job, another advantage or by making threats — that is breaking the law,' said Denis Dion, a spokesman for Quebec's chief electoral officer Marcel Blanchet.

Zambito's company, Infrabec, has been awarded more than half the public works contracts in Boisbriand in the past five years.

Saint-Jean denied showing any favouritism towards Zambito's company in awarding the municipality's contracts.

In a written statement issued late Thursday night, she said that two separate investigations by the Canadian Competition Bureau and Quebec's Municipal Affairs Ministry concluded no favouritism was shown towards Infrabec.

Boisbriand is a 40-minute drive north of Montreal. (CBC)She also denied working with him to call down her campaign rivals.

Saint-Jean does admit she met last spring with Zambito and two city councillors with mayoral ambitions — Marlene Cordato and Patrick Thiffault — to discuss the fall municipal elections.

Saint-Jean said she agreed to meet with her potential opponents for the election to try to negotiate an election deal, in order to save taxpayers an estimated $300,000 in campaign costs.

During the meeting, Zambito allegedly tried to convince Cordato and Thiffault to accept a deal that would allow Saint-Jean to be re-elected without opposition.

Cordato and Thiffault recorded the meeting, and handed the tape over to Enquête reporters.

Zambito did not return Radio-Canada's calls.

The allegations come as another Radio-Canada investigation suggests widespread collusion in Quebec's construction industry.

The separate Enquête investigation alleges a select group of construction companies has controlled bidding and inflated prices on major municipal infrastructure projects in and around Montreal, and other major Quebec cities, boosting costs by as much as 35 per cent.

The Quebec government is set to release billions of dollars to modernize road infrastructure.