TORONTO -- Ontario's Liberal government on Thursday compared its move to cancel gas plants in Oakville and Mississauga with the United States' decision in the early 1960s to land a man on the moon -- both plans were enacted without knowing the actual costs.

Liberal Bob Delaney, the parliamentary assistant to the minister of energy and a member of the committee holding public hearings into the gas plants, admitted the government scrapped the energy projects with no idea what the total bill would be.

"Just the same way as when the United States committed to go to the moon, they didn't know how much it was going to cost," Delaney told reporters.

Delaney's comment prompted both opposition parties to play off the moon landing theme when attacking the Liberals for low-balling the $275 million cost of scrapping the Mississauga project by $85 million.

"According to Mr. Delany, the costs are going to go through the roof right to the moon," said PC energy critic Vic Fedeli.

"I am sadly shocked again that first they didn't know the costs, but they'd agreed that once they did know the costs, they're going to cover it up."

The Liberals didn't care how much it would cost to save seats in the heavily-populated areas west of Toronto where the gas plants were extremely unpopular, said NDP energy critic Peter Tabuns.

"They pushed the button, they launched this one without giving any thought to the people of Ontario and how high they were going to drive their hydro bills," he said.

During question period, Tabuns continued the moon shot theme as he accused the Liberals of continually low-balling costs even after they were given updated figures from the Ontario Power Authority last summer.

"Well, by July, the eagle had landed and the costs were known, but for nine months the Liberal government has been telling Ontarians the cost was something otherwise," said Tabuns.

The auditor general reported earlier this week that the cancellation of the Mississauga gas plant cost $275 million, not the $190 million the Liberals claimed, casting doubt on the government's $40 million price tag for cancelling the Oakville project.

The justice committee has already heard the cost of cancelling that project could be increased by hundreds of millions of dollars just to deliver gas to the new site for the plant in Napanee.

"The OPA told us that's going to add up to $476 million just for gas supply and management costs, plus transmission costs," said Fedeli.

"The Oakville plant could likely come in at $991 million, if the OPA's numbers are accurate."

Former energy minister Chris Bentley, who quit politics earlier this year after being at the centre of the storm surrounding the cancelled gas plants, will appear at the justice committee hearings next Tuesday.

Bentley was not named energy minister until after the 2011 election, but he was the target of an opposition contempt motion when the Liberals initially refused to release all the documents on the energy projects that were requested by the committee.

Current Energy Minister Bob Chiarelli said Thursday part of the reason the cost for the gas plants was so high is because the opposition-dominated committee forced the minority government to release all the documents before new deals were negotiated with the developers of the projects.

"We were not in a very good bargaining position, mainly because the opposition forced us to show our hand and put all the documents on the table, and therefore compromised our bargaining position," said Chiarelli.