Canada’s largest federal public sector union is threatening legal action as the government moves to increase public servants’ in-office time.

The federal government is ordering public servants to be in the office at least four days a week starting in July, while executives are expected to return to the office full-time in May.

The Public Service Alliance of Canada says changing remote work rules in the middle of ongoing contract negotiations is “grounds for legal action.”

A statement from the union says it will be fighting the decision “every step of the way” and that it is prepared to take legal action against changes to the in-office mandate.

The union says “nothing is off the table.”

The federal directive applies to public servants working in the core departments and agencies under Treasury Board, though the Canada Revenue Agency has said already it intends to follow the same approach.