Ontario's auditor general will examine millions of dollars in government payouts to teachers' unions to cover negotiating costs.

The Liberals supported a Progressive Conservative committee motion that requested the auditor general review the payments and report on where the money came from and what it was intended to fund.

The Liberal government paid $3.74 million to various teacher and support staff unions in the 2008, 2012 and in the current rounds of contract talks as the government transitioned to a new bargaining system.

Education Minister Liz Sandals originally said the payouts were made without receipts from the unions to show their costs, but Premier Kathleen Wynne later said the government would ask for receipts.

Progressive Conservative Lisa MacLeod, who introduced the motion, says "it doesn't look good" that such large sums of money were promised to the unions undocumented.

The Tories say Auditor General Bonnie Lysyk will present her report by the spring of 2016.