MONTREAL -- An alliance of construction trade unions broke off negotiations with a group representing employers on Sunday, saying it prefers to wait for the province to adopt back-to-work legislation.

Union spokesman Michel Trepanier confirmed in a phone interview that the unions had rejected what the construction companies called their final offer.

"We were laughed at, we were in good faith from the beginning, now today we say it's over," he said.

Trepanier is calling on construction workers to demonstrate in front of Quebec's legislature on Monday, where the government is expected to begin pushing through the back to work bill.

He said they're asking Premier Philippe Couillard's government to weigh its priorities carefully.

"(The government) will have a choice tomorrow between the construction workers and their families, and the bosses and their chums," he said.

About 175,000 workers launched the strike on Wednesday, crippling activity on major projects such as the Champlain Bridge and a Montreal superhospital.

Work schedules and overtime are believed to be at the heart of the dispute regarding the industrial side, while salaries are the main stumbling block in the residential sector.

Negotiations appeared to hit a wall at both negotiating tables on Sunday, beginning when a group representing employers in the residential sector withdrew from the talks, claiming the union's demands were "unacceptable."

Spokesman Francois William Simard said the construction companies were disappointed the unions rejected what he called a generous offer that included a 1.9 per cent wage increase over the next four years.

He called on the Quebec government to consider the ability of employers and citizens to pay for its legislation.

"We hope we will have something reasonable, because frankly at the end, in the residential sector, there's no hiding that if there are wage increases that are too high, it's quite simply the citizens who will pay," he said.

Later in the day, the group representing the industrial sector laid out its final offer to the unions, which a spokesman described as a "win-win."

Eric Cote said the offer included concessions on several key issues, including work-life balance and working on Saturdays.

"In the proposal, it would be possible, if accepted, for all workers in the institutional, commercial and industrial construction industry to work a four-day weekly schedule," he said.

This is the second general strike in the Quebec construction industry in four years.