The Public Service Alliance of Canada (PSAC) says it will file a complaint with a the Federal Public Sector Labour Relations and Employment Board over the government's hybrid return-to-the-workplace plan announced last week.

Starting March 31, federal public servants will be required to work at least two to three days a week, or between 40 and 60 per cent of their regular schedule, in person. Many employees have been working from home since the COVID-19 pandemic struck nearly three years ago.

"In-person work better supports collaboration, team spirit, innovation and a culture of belonging," Mona Fortier, president of the Treasury Board, said Dec. 15.

"We've now seen that there needs to be greater fairness and equity across our workplaces and we need consistency in how hybrid work is applied across the federal government."

But in a statement released Wednesday, PSAC, which represents nearly 230,000 workers in every province and territory, said it's the government's policy that is unfair.

"The federal government's blanket hybrid work plan tramples on workers' collective bargaining rights and forces a flawed one-size-fits-all approach on a diverse and evolving public service," the union said.

PSAC said it will file a "statutory freeze complaint" against the Treasury Board and other agencies for "unilaterally imposing changes to our members' working conditions" while the union is engaged in labour negotiations on behalf of 165,000 federal public servants.

"Making changes to working conditions while those very same issues are at the bargaining table is against the law," PSAC said.

The union said it's also providing guidelines to help its members file their own grievances once the policy is made official on Jan. 16.

According to PSAC, more than 80 per cent of its members who were surveyed oppose the government's hybrid work plan and are prepared to take action, including strike action, "to fight for better work-life balance, fair wages, protections against harassment and discrimination in the workplace and other top bargaining priorities."

Last week, Fortier said various departments have experimented with different hybrid models to arrive at a workable return-to-the-office plan.

"I understand that there were conversations and feedback shared," she said. "We informed the unions about this new decision from the management, that location of work is a right of the employer."

A PSAC spokesperson told CBC the union plans to file the complaint by the end of the week.

The Federal Public Sector Labour Relations and Employment Board is an independent, quasi-judicial tribunal responsible for administering the collective bargaining and grievance adjudication systems in the federal public service and in Parliament.