The City of Winnipeg and its largest union are trading accusations of bad-faith negotiations as the two parties try to hammer out a collective bargaining agreement.

The Canadian Union of Public Employees Local 500, which represents more than 5,000 city workers, plans to file a complaint to the Manitoba Labour Board next week about the City of Winnipeg.

CUPE 500 president Gord Delbridge said he does not believe the city has bargained in good faith since the last collective bargaining agreement expired late in 2016.

"They're putting so many roadblocks up, we feel we can't bargain in good faith. They've presented us with so many challenges, we feel we can't move forward," Delbridge said in a telephone interview Saturday.

Delbridge said the roadblocks included an "unprecedented proposal package," but said he could not divulge details due to the confidential nature of negotiations.

The city, meanwhile, has already filed an unfair labour-practice complaint against CUPE 500. Chief corporate services officer Michael Jack said the city asserted on Feb. 27 that CUPE was refusing to bargain in good faith.

"On the second scheduled day of bargaining, CUPE walked out of negotiations after just seven minutes at the table and refused to allow the city's bargaining team to go through its bargaining proposals and provide explanations," Jack said Saturday in a statement.

This led the city to seek help from a conciliator, who was appointed the next day, he said.

"On the first day of conciliation, CUPE again refused to meet face to face and bargain in good faith, which is making the conciliation process extremely challenging," Jack said.

"The city recognizes the important work performed by all of our staff in CUPE, and remains committed to finding a fair and reasonable solution to these ongoing negotiations. We look forward to resuming negotiations with CUPE, and coming to an agreement that is fair and reasonable to all parties, including Winnipeg taxpayers."

Delbridge said some of what the city has proposed during negotiations would significantly hinder operations. Delbridge placed much of the blame on a new city labour-relations manager. "He's been a real challenge to deal with," he said.

The CUPE leader said he heard similar complaints about the city's negotiating tactics at a meeting of city union leaders on Friday. Unions representing the city's police officers, paramedics, transit workers and professionals were also in attendance, he said.

A total of five city unions have been without contracts since December and talks with four are at a standstill. The city has asked for a conciliator to assist talks with CUPE 500, while the Winnipeg Police Association, the United Fire Fighters of Winnipeg and the Winnipeg Association of Public Service Officers have requested arbitration.

On Wednesday, Winnipeg Mayor Brian Bowman refused to say whether the city is playing hardball with its unions.

"We have an obligation to ensure that the mandate that is provided to our new chief negotiator is fair and reasonable to our valued employees, but also protects the bottom line of taxpayers. We're trying to achieve both," Bowman said.

Delbridge said CUPE does not have a strike vote planned.

"We've never been on strike before. I'm one who thinks we should negotiate and get to a deal," he said.

"If they're pushing for a strike, that alone would be in bad faith."

Jack said the city has zero interest in a labour stoppage.

"We know full well a strike or a lockout can not only be massively damaging, in a way that people can't predict, but can leave scars that can last a very long time," he said in a telephone interview.