A union representing federal government workers has temporarily called off talks with the Harper government, accusing the Conservatives of acting illegally to change sick leave provisions for civil servants.

The Public Service Alliance of Canada walked away from bargaining meetings that were scheduled for this week after the government introduced proposed changes to sick leave as part of its budget implementation bill.

Bill C-59, introduced Thursday, would give the government the ability to unilaterally create a new short-term and long-term disability program.

Proposed changes to the sick leave provided to federal civil servants are among the most contentious issues at stake in contract talks with public service unions, including PSAC.

If the budget implementation bill in its current form becomes law before Parliament rises for the summer, the federal Treasury Board Secretariat will have the power to establish and modify the "terms and conditions of employment related to the sick leave of employees."

Robyn Benson, the union's national president, says that goes against the Charter of Rights and Freedoms, and her union will use every legal means necessary to oppose the provision.

Treasury Board President Tony Clement has said on numerous occasions the Harper government wants to continue bargaining for a new collective agreement, and called Monday's move by the union "very unfortunate."

Budget savings 'set in stone'

The April 21 budget included savings of $900 million in the current fiscal year from savings generated through the negotiating process.

Pierre Poilievre

Pierre Poilievre has told CBC Radio's Ottawa Morning that federal budget savings related to the public service are not fluid. (Justin Tang/Canadian Press)

Clement has suggested that number is a soft target, but Employment Minister Pierre Poilievre, who represents an Ottawa-area riding where many federal civil servants live, has insisted the savings budgeted by the government are "set in stone."

Failing to reach that target would remove a large chunk from Finance Minister Joe Oliver's projected $1.4-billion budget surplus for 2015-16.

The Conservatives have maintained that current sick leave provisions have created a huge liability on the government's books because of the amount of sick time that civil servants have accumulated over the years.

But PSAC maintains that the liability doesn't exist.