QUEBEC -- The Quebec Liberals defended their back-to-work bill Tuesday from accusations the law gives to much power to the government regarding negotiations between unions and private-sector construction companies.

Members of the legislature debated through the night and passed a law forcing Quebec's 175,000 construction workers to end their week-long strike and return to work Wednesday.

The law grants workers a pay hike of 1.8 per cent and forces both sides to enter into a five-month mediation period followed by an arbitration process if a deal cannot be reached.

Unions said their lawyers are preparing a legal challenge to the law because they feel the government has potentially illegally limited their right to strike.

The association representing construction companies, meanwhile, said the unions got the better deal because the law grants workers a pay raise without forcing them to give up anything in return.

Both sides, however, criticized the fact the government has given itself the right to decide what issues will be decided in arbitration -- if it comes to that -- and what subjects get left out.

Opposition leader Jean-Francois Lisee during question period called the law "anti-worker."

He said the government is in a conflict of interest because it can now decide what subject matters enter into arbitration while also being the body that awards the most construction contracts in the province.

Premier Philippe Couillard responded by saying the government has accepted to consult with all parties before any potential arbitration process begins.

Eric Cote, spokesman for the association representing private-sector construction companies, said "we are preoccupied that the arbitration process is at the mercy of political powers."

He said what is subject to arbitration "can be motivated or subject to political pressure."

A coalition of construction labour unions said representatives were not available Tuesday, but issued a news release saying the government has "muzzled" workers with the new law.