Canada's largest federal public-service union has left the bargaining table but says it is standing by to resume negotiations when the federal government comes back with a new offer. 

Federal workers were hitting the picket lines across the country on Wednesday after Canada's largest federal public-service union and the government failed to reach a deal by a Tuesday evening deadline.

On Wednesday morning, Prime Minister Justin Trudeau said negotiations had paused. 

"Obviously, Canadians have a right and deserve to get the services that they need from the federal government. That's why we need the management and labour to get back to the bargaining table as soon as possible, and continue to make progress," Trudeau said. 

In a statement, Public Service Alliance of Canada national president Chris Aylward said "bargaining teams are standing by and ready to bargain when the employer comes back to the table with a new mandate." 

A late Tuesday news release from the Treasury Board of Canada Secretariat says the government and the Public Service Alliance of Canada are still at odds when it comes to key contract issues for both sides. 

The bargaining groups involve some 155,000 federal public servants, including 35,000 Canada Revenue Agency workers.

With picket lines expected to be set up Wednesday at some 250-plus locations, the union is calling the strike action, which officially began at 12:01 a.m. EDT, one of the largest in Canadian history. 

The union's national president Chris Aylward said during a brief news conference in Ottawa on Tuesday night that despite the move, union officials are still hopeful and the goal is to get a tentative agreement.

Federal workers arrived Wednesday morning on Parliament Hill to picket, holding signs that say "fair deal for workers." 

NDP Leader Jagmeet Singh met with union members to offer his support and took photos with them. In an interview, Singh put blame on the federal government for failing to deliver a "fair deal." 

"These are workers that were the ones that delivered so much important supports for Canadians when we needed it most in the pandemic," Singh said. "And now they deserve respect."

Singh said he's made it clear to the Liberal government that the NDP will not support back-to-work legislation. 

Treasury Board President Mona Fortier said Wednesday morning that she's hoping some progress can be made in negotiations today. 

"I am convinced that we can," Fortier said. 

Fortier wouldn't weigh in on the possibility of back-to-work legislation. 

Wage increases have been top of mind at the table, with the union pushing for annual raises of 4.5 per cent over the next three years. It says the increases are necessary to keep pace with inflation and the cost of living. 

The Treasury Board says it has offered the union a nine per cent raise over three years, on the recommendation of the third-party Public Interest Commission.

Since the strike involves nearly one-third of all federal public servants, both the union and the government have warned of disruptions, including what could amount to a complete halt of the tax season. 

Other concerns include slowdowns at the border and disruptions to EI, immigration and passport applications.

Initial negotiations began in June 2021, with the union looking for a new contract. The union declared an impasse in May 2022 and both parties filed labour complaints. 

Mediated contract negotiations began in early April of this year and continued through the weekend in what the union described as the government's last chance to reach a deal.

This report by The Canadian Press was first published April 19, 2023.