A Montreal-area engineer who testified about an ingrained system of payoffs and bid-rigging on municipal construction contracts finished his time on the witness stand with a teary address this morning.

The president of Génius-Conseil, formerly known as Groupe Séguin, Michel Lalonde told the Charbonneau commission he understands the consequences of his actions over the six years that he said he was part of an arrangement to fix public contracts in exchange for political donations as well as illegal payments to other elected officials.

Lalonde said he regrets what he did and hopes one day he'll be forgiven.

"I can't erase the past or the events that I participated in," he told the commission.

He said at the time, he believed he took the best course of action for his business and his employees.

Before he read his written statement, commission chair France Charbonneau thanked Lalonde for his six days of testimony.

"It's essential that people of your standing work with us," she told Lalonde. "We acknowledge that it took a great deal of courage to testify publicly and once again, we thank you."

During his time on the witness stand, Lalonde told the commission he felt he had no choice but to make illegal donations to the campaigns of elected officials. Without those donations, he said, his company wouldn't have obtained public contracts.

He described in detail an arrangement made with former Union Montréal treasurer Bernard Trépanier, which, Lalonde claimed, fixed the tendering process so firms that had already agreed to pay back three per cent to the party would win bids.

Lalonde also described giving cash donations to borough mayors and other elected officials in exchange for preferential treatment in the awarding of contracts.

Several of those mayors have denied taking any money from Lalonde. Others have said the donations were made legally.

During his time on the witness stand, Lalonde told the commission how associates at his firm and some of their spouses bought tickets to fundraising events for provincial political parties and later had those donations reimbursed in cash or through company bonuses.

Quebec's political donation rules prohibit companies from reimbursing employees for donations. Contributions need to be made by individuals and within the limit set by government legislation. Lalonde admitted that some of those reimbursed claimed the repaid donations for credit on their income taxes.

Lalonde testified that he also gave cash and gifts to a member of a Transport Quebec selection committee when his firm won a $3 million contract for highway work.

After two days of cross-examination, the engineer left the stand on an emotional note, when addressing the impact his public testimony has had on his family.

"I'd like to acknowledge the support of my family, my parents, my wife, my four kids, who have gone through a lot in the last few days," he said, struggling to hold back tears.

"It was because of their support that I could continue with my testimony and tell the truth to the commission."

The commission's next witness is Jacques Victor, a expert in the tendering process. His testimony is expected to focus on a controversial east-end development project, which is also the subject of a criminal case awaiting trial later this year.

Because of those ongoing criminal proceedings, Victor's testimony will be covered by a temporary publication ban.