TORONTO - Ontario voters won't have to wait until an auditor general's report due late this summer for an updated estimate on the cost of cancelling a gas plant in Oakville.

The opposition parties reject the government's claim that it cost $40 million to scrap the Oakville gas plant, especially since the auditor reported that the Liberals low-balled the cost of cancelling another plant in Mississauga by $85 million.

Last week, Premier Kathleen Wynne insisted it would be wrong for the government to provide an updated cost for the Oakville project before the auditor completes his investigation, expected by August.

However, the Liberals now say they want to call the CEO of the Ontario Power Authority to committee this week to, in the government's words, "share their current estimate of longer term costs and savings" associated with the Oakville plant.

The Progressive Conservatives and New Democrats estimate the cost of cancelling the Oakville gas plant will be closer to $1 billion.

Former energy ministers Chris Bentley and Brad Duguid will both testify later Tuesday at the justice committee hearings into the cancelled gas plants.