Quebec's striking construction workers will almost certainly be returning to work on Tuesday morning after members of the National Assembly held a rare holiday weekend session to adopt back-to-work legislation.

Three of Quebec's four parties supported a legislated end to the two-week strike of 77,000 institutional, commercial and industrial construction workers. But they spent the weekend, including an all-night debate, bickering about the details.

The governing Parti Québécois proposed an 8.6 per cent pay increase over four years and leaving all other terms of the contract untouched.

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The opposition Liberals and Coalition Action Québec, for their part, demanded a one-year deal that makes pay adjustments only for cost of living increases in the hope that will entice the parties to return to the bargaining table. The Liberals later backed down, saying they would accept a 2 per cent pay increase this year. The small Québec Solidaire party said it would vote against any imposed settlement.

The proposed law includes stiff penalties for those who stage wildcat strikes and refuse to return to work. The fines range from $100 a day for individual workers to $125,000 a day for a union or employer's association that refuses to respect the terms of the imposed deal.

When debate on the proposed law, Bill 54, began on Sunday evening, it was adopted in principle by a vote of 102-1. But the opposition parties vowed to propose amendments to the terms, and that debate was slated to last all night with a final vote early Monday morning.

Quebec Labour Minister Agnès Maltais said the opposition demands were "irresponsible" and threatened to withdraw the legislation altogether.

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She argued that granting the workers any less than the 8.6-per-cent wage increase would create a "dangerous disequilibrium" on work sites. But the Labour Minister also toned down her rhetoric as the evening wore on, saying everyone wants a negotiated settlement.

There are 175,000 unionized construction workers in Quebec, and their unions negotiate provincewide contracts in three large blocks.

Two of those blocks have already negotiated settlements.