OTTAWA - The Conservative government decided to play referee on the dispute between Canada Post and its locked out workers Monday, but one side is already crying foul.

The bill could also spark one of the first battles with the Opposition, with the NDP vowing that it would delay passage of the bill.

The Tories introduced back-to-work legislation to force the resumption of postal services across the country but included in the bill are wages that are even less than what Canada Post was offering employees.

The Canadian Union of Postal Workers says their employer's last offer was for increases of 1.9 per cent in 2011, 2012 and 2013, and 2.0 per cent in 2014.

The back-to-work legislation sets wage hikes at 1.75 per cent in 2011, 1.5 per cent in 2012, 2 per cent in 2013 and 2014.

"Imposing wage increases that are lower than Canada Post's last offer punishes postal workers for a disruption that was caused by the corporation's national lockout," said union President Denis Lemelin in a statement.

Labour Minister Lisa Raitt said that the wages were reflective of the agreement the federal government has with its own unions.

The postal union's sharp reaction to the wage provisions of the bill followed criticism from labour relations experts and opposition politicians that the Conservatives already weren't playing fair by getting involved in the lockout in the first place.

The NDP slammed the bill, saying that it trampled on workers' rights, citing the lower wages offered in the bill.

"They are building a precedent here by saying, 'Look, if you don't like what the employees are telling you at negotiations, just stand by and we will legislate them back to work'," said NDP labour critic Yvon Godin to Canada AM on Tuesday morning.

"I think Stephen Harper hates the workers," Godin said.

It was the second time in a week that the Harper government stepped in to end a labour dispute.

Last week, they introduced back-to-work legislation to get Air Canada and its employees to make a deal. One was announced before that bill came into effect.

"Without any public policy debate, we now have a new bargaining regime," said George Smith, a fellow in the Queen's University School of Policy Studies and labour relations expert.

"I don't think this was a platform of the Harper government. It surprises me that without that debate, that they have decided in two cases where there is clearly not overwhelming evidence of economic harm that they will intervene and impose upon the parties a process that is not contemplated in the Canada Labour Code at this point in time."

Canada Post suspended urban postal operations countrywide last Wednesday after nearly two weeks of rotating strikes by the union.

The two sides made no progress in their talks over the weekend, and it had been uncertain whether talks scheduled for Monday would actually take place.

Raitt had signalled last week the bill was coming and introduced it after question period Monday. It is what's known as final offer arbitration, each side will be required to submit what they believe is their best offer and an arbitrator will pick the best one.

Raitt said earlier Monday she hopes that the bill either passes before the Commons rises for the summer on Thursday or that the two sides work out their own solution before then.

"Canadians want certainty, they want to know that their mail is going to continue to be delivered or start to be delivered once again, and that's what we are here for," she told reporters.

Canada Post says the job action has already cost it $100 million in lost revenue.

The Crown corporation has said the main sticking point in the dispute is the union's demand for staffing levels beyond the capability of Canada Post, adding that wages were not the key disagreement.

The union has been emphasizing working conditions and safety issues, as well as arguing that new employees would receive inferior wages and pensions.

Postal workers marched at a number of rallies across the country Monday from Kamloops, B.C., to Labrador City, N.L., to gain public support for their cause.

Workers and their supporters in Vancouver, Edmonton and Winnipeg also said they occupied the offices of Conservative MPs.

"We've done everything in our power to achieve a negotiated settlement with as little disruption to the public as possible," Mike Palacek, a postal worker from Vancouver, said in a news release.

"Canada Post's response has been to suspend all of its services, lock us out, and wait for back-to-work legislation."

Workers were delivering pension and social assistance cheques Monday, despite the lockout, the union said in a statement.

A spokesman from Canada Post said Monday morning they believed a deal could still be reached.

"There is time to sit down and hammer out a deal but that requires a commitment to bargain that we haven't seen from the union," said Jon Hamilton.

Going to final offer arbitration is generally seen as the option of last resort and Raitt said the government felt it had no choice.

"It's the appropriate way to deal with this one because the parties have been negotiating on the matter for months,'' said the minister.

"It's been exhaustive how much help they've had, how much time they've had and they are unable to even close it a little bit. So now it is time for the arbitration to happen and happen in a clean and clear way and then we get back to working on the economy.''

The federal government legislated striking postal workers back to work in 1997, the last time the union went on strike, after they were off the job two weeks.

The government has used back-to-work legislation over 30 times since it was first deployed in 1950, ending a rail strike that threatened to empty store shelves as merchandise had no way to get across the country.

Air Canada employees were on strike less than a day before the government introduced back-to-work legislation last week and the airline never stopped flying.

Labour relations history in Canada dictates that the government should play as neutral a role as possible, said Laurel Sefton MacDowell, a labour relations historian at the University of Toronto.

The Canada Post and Air Canada intervention signal a shift, she said.

"Basically, they are putting their clout behind management, which means they are intervening in a way that is shifting the balance of power," she said.

Opposition New Democrats also accused the Conservatives of trampling on the process of collective bargaining, saying Canada Post's lock-out of employees was what crippled the mail service, not the rolling strikes by postal workers.

"It is the government itself, through a Crown corporation, that caused the lock-out of the employees," said NDP MP Thomas Mulcair.

"This same government is now turning around and criticizing a situation that it created itself.''

The possibly that back-to-work legislation could be brought in to end a labour dispute leaves management with little incentive to negotiate, critics and union officials say.

But the final offer arbitration method of having one side win over another doesn't help either in the long run, said Smith.

"Think of all the situations in life when decisions have to be made, some of them very difficult, and you imagine it's take-it or leave it, one of two choices gets made, and the other party doesn't get what they want,'' he said.

"There is a relationship issue there that will ultimately come out of this."

Stephanie Levitz, The Canadian Press, with files from the Huffington Post Canada