Members of Parliament were continuing to debate back-to-work legislation for postal workers past midnight as politicians stared down the possibility of an all-night debate on sending Canada Post employees back to work and ending a lockout.

The NDP started speaking in an attempt to stall the bill, with NDP Leader Jack Layton starting around 9 p.m. Thursday.

His speech, in its opening minutes, touched on the commitment of postal workers, the repetitive stress injuries some of them suffer, the Charter of Rights and wind turbines.

Rumours were flying prior to an 8:15 p.m. procedural vote that the NDP and Conservatives had reached a deal to remove the controversial salary provisions from the legislation.

But MPs seemed to be settling in for a long night, with Liberal MPs instructed not to leave the parliamentary precincts to sleep, and to sleep fully clothed in case they are called back for a vote.

The House of Commons won't rise for its summer break until the legislation is passed.

How long it takes is up to the NDP. The Official Opposition could delay the vote by putting up all of its 103 MPs as speakers. But one thing the NDP caucus has to take into consideration is that Friday is St-Jean-Baptiste Day, a holiday in Quebec.

Minister of Labour Lisa Raitt says back-to-work legislation is needed because Canada Post and its locked out workers can't come to an agreement, and the labour stoppage is threatening the Canadian economy. Adrian Wyld/Canadian Press

Quebec interests weigh heavily on the NDP because 59 of its MPs are from that province and they helped propel the NDP from its fourth-place position in the House of Commons to second in the May 2 election.

Earlier, Labour Minister Lisa Raitt said the Conservative government was open to changing its back-to-work legislation,

"If they have real amendments, they should present them to us and we'll take a look at them … we're open to take amendments. You have to consider them. That's part of debate," said Raitt.

Layton had suggested in question period the government remove a controversial section of the bill that would give the union a lower salary than the one proposed by management in the last round of talks. The NDP plans to move an amendment to the bill Thursday evening to take out the salary portion.

But Prime Minister Stephen Harper said the offer is fair.

"The wage rates set in the bill are only fair. They reflect what we've negotiated with federal public servants," Harper said. "The role of the Canadian government is to act in the higher interest of the Canadian population and the Canadian economy, not in the interests of those that are around the table."

Layton said Canada Post has no reason to negotiate when the government is offering a lower salary than the corporation's management.

"The prime minister has rendered collective bargaining pointless in this country… Why bother to bargain?" he said. "It's a terrible precedent."

Harper shot back, accusing the NDP of taking the union's side.

"The government, unlike the NDP, is not beholden to one of the parties at the table. The government represents the wider interests of the Canadian economy," he said.

Canada Post said in a statement that the two sides remain "far apart" on several issues.

Government defends back-to-work bill

As debate on the motion began Thursday morning, Labour Minister Lisa Raitt fended off accusations from the opposition that the government was being heavy-handed.

Raitt said the parties have been unable to reach a deal on wages, pensions, short-term disability benefits and other contract issues, and that the government had to step in because the dispute is affecting the Canadian economy.

"There were significant issues on the table that they simply cannot close the gap on in a short period of time. It is affecting the Canadian economy and Canadian citizens and we are acting," she said.

The government introduced the back-to-work legislation Monday, and was quickly criticized for its design. The bill sets out wage increases that are less than what Canada Post had offered to its workers, a measure the opposition parties keep hammering the government over.

Raitt defended the move Thursday saying they are the same wages as the government has previously negotiated with the largest public sector union and that they are "appropriate, fair wages."

On the other issues aside from salary, the bill would force the two sides into final offer selection binding arbitration, meaning each side tables its final offer and the arbitrator picks one or the other.

The union is opposed to the final offer selection process, but Raitt defended it Thursday during debate.

"We believe that's the most appropriate way to deal with the matter," she said, adding that it will mean a "clear, crisp decision."

Union wants amendments to bill

The union told CBC News that it has asked the opposition parties to propose amendments to Bill C-6 so that the outstanding issues would be decided by mediation, not final offer selection.

The Liberals have indicated they will propose an amendment but its exact nature won't be known until later in the day Thursday.

The labour dispute began earlier this month with rolling strikes by union members, who were then locked out by Canada Post on June 14.

Members of Parliament are feeling the heat over the Canada Post issue. Thursday morning, about a dozen people staged a protest at the office of Foreign Affairs Minister John Baird. They were not members of CUPW but said they were there to occupy Baird's Ottawa office in support of the postal workers.

Another Conservative MP, Shelly Glover, has encountered similar incidents and earlier this week closed her constituency office in Winnipeg because of protests.