The 2015 budget unveiled Tuesday by Finance Minister Joe Oliver listed $900 million in savings in the current fiscal year from proposed changes to public service accumulated sick time.
Critics called the move political sleight of hand, considering the fact that negotiations are ongoing.
But the government doesn't necessarily expect to realize the full $900 million in savings, Treasury Board President Tony Clement said Wednesday after the weekly Conservative caucus meeting.
"The budget is the budget, and the savings are the savings," Clement said. "But there is some breathing room for me recognized in that calculation."
The government has told civil service unions it expects to eliminate the system that allows public servants to bank sick days and carry them over from year to year.
Ottawa is hoping instead to provide short-term disability benefits through an insurance company.
Talks have been going on for the last year and are expected to last until at least June with 47 meeting days scheduled to take place, on top of the nearly 200 negotiating sessions that have been held so far.
Clement said he wants to bargain in good faith, even though the government is already counting the $900 million in savings from future sick leave liability toward its projected $1.4-billion surplus in 2015-16.
"They clearly want a Liberal or an NDP government to negotiate with, who will roll over and accept their positions," Clement said of the unions with which he is bargaining.
"I'm here for the taxpayer," he said. "I'm here also for the public servant who wants to work hard, who needs sick benefits when they are truly sick."
Public Service Alliance of Canada national president Robyn Benson called the budget an attack on the collective bargaining process, denouncing its "go to work sick" plan as a step in the wrong direction.
"Our focus is always to strengthen public services and ensure a healthy workplace," Benson said.
"The government is threatening to derail an ongoing bargaining process that was delivering positive results for the government, our members and the Canadian public."
More than 700 of the union's leaders will decide next week on next steps when they meet at the PSAC national convention, beginning April 26 in Quebec City.