Nova Scotia's Liberal government finally moved on a contentious piece of labour legislation Tuesday, effectively imposing a wage package on 75,000 public sector employees.

Premier Stephen McNeil said the proclamation of the Public Services Sustainability Act was being done in the "best interests of Nova Scotians."

The act was passed in December 2015 to ensure third party arbitrators could not bind the government to wage settlements. At the time, McNeil promised it would not be brought into force until it was needed.

The government's move came two weeks after the Nova Scotia Government and General Employees Union — the province's largest — filed for arbitration on behalf of nearly 8,000 civil servants after last-ditch conciliation talks broke down.

"I've made it very clear that an unelected, unaccountable arbitrator will not determine the taxpayer's ability to pay," McNeil told reporters.

The act doesn't end arbitration but does provide the guidelines for wages included in a contract.

The act sets a wage pattern of three per cent over four years that will allow increases of one per cent in the third year of the contract, followed by 1.5 per cent in the fourth year and 0.5 per cent on the final day of the package.

It also freezes a retirement allowance retroactive to April 1, 2015. The so-called public service award is a lump sum payment for retiring workers with at least 10 years of service.

New employees will no longer be eligible for the payment under the government's change.

McNeil said the act will be referred to the Nova Scotia Court of Appeal under the Constitutional Questions Act to obtain an opinion.

He said the government is confident the law will stand up to constitutional scrutiny.

"We believe the constitution says that everyone is entitled to open and free collective bargaining. We believe we've gone that process. We have been at the table many times with our (bargaining) units," he said.

The act exempts groups that already have agreements, including doctors and teachers, and about 15,000 management and non-union positions.

McNeil was asked whether he believed his party's re-election May 30 was an endorsement of his approach to the labour file.

"This has been an endorsement on the direction of our government. We also know that Nova Scotians wanted our government to live within its means and they believe the approach that we were doing was a positive one."

Progressive Conservative Leader Jamie Baillie said the government's move is part of "an expensive game."

"We are now condemned to years of legal costs," Baillie said. "Millions of dollars that's not going to go to doctors or health care because the government couldn't get the job done in the normal way and has resorted to this kind of gamesmanship."