TORONTO -- Ontario's opposition parties welcomed a move by Kathleen Wynne Thursday to ask the auditor general to broaden his examination of cancelled gas plants, but said they still want committee hearings into the controversy.

The premier-designate asked Auditor General Jim McCarter to add the cancelled gas plant in Oakville to his current probe of the Mississauga project -- two decisions that cost taxpayers at least $230 million.

The Conservatives and New Democrats said the auditor doesn't have the power to get answers to all the questions surrounding the Liberal government's politically-motivated decisions.

"The auditor general does not have the capacity to get at some of the very important information that we need: who was making the decisions to cancel the gas plants, where did the directive come from, are all the documents out," said NDP Leader Andrea Horwath.

"There's a lot of things that the auditor general simply cannot do."

Progressive Conservative Leader Tim Hudak also questioned the auditor general's power to get to the bottom of the gas plants scandal.

"While the auditor can look at expenses ... he does not have the authority to subpoena individuals who gave the orders to cover up information," said Hudak.

"I do have a concern that this may simply be an attempt to kick it down the road and maybe it'll be up to the next government to actually get the answers for taxpayers who are stuck with the bill."

McCarter, however, said the request to probe the Oakville project would not delay the report into the Mississauga gas plant beyond its expected release in late March or April.

The report into the Oakville plant would come months later, added McCarter.

"We'll start doing a bit of work on the Oakville one while we're wrapping up the other one because we'll get some economies of scale by doing that, but basically it would almost be two separate projects," he said.

An opposition-dominated committee asked the auditor to investigate the Mississauga gas plant cancellation before Premier Dalton McGuinty prorogued the legislature last October, effectively killing committee hearings that were set to begin the next day.

Horwath said it was the Liberals that stopped the committee from requesting that the Oakville plant be included in the auditor's probe in the first place.

"They stubbornly refused to do it up until now," she said.

That committee needs to restart its work as soon as the legislature returns Feb. 19, said Hudak.

"I think the best way forward is to immediately reinstate that committee to get those types of answers, and I hope that the new premier will be onside with that," he said.

Horwath called it "a mistake" for Wynne to rule out an NDP request for a public inquiry into the cancelled gas plants, and warned the issue would have to be dealt with one way or another by the legislature, despite the auditor's expanded investigation.

"Ultimately the people deserve the answers and the Liberals need to be accountable for the decisions that they made," said Horwath.

The Conservatives and New Democrats started demanding hearings into the Liberals' decision to cancel the generating stations just hours after Wynne won her party's leadership Jan. 26.

The Tories had threatened to again raise the contempt of Parliament charge against Energy Minister Chris Bentley if there are no hearings when the legislature returns.

The rare contempt motion, which led to nasty, personal attacks during debates, all but tied up legislative business last fall, and was one of the reasons cited by McGuinty when he prorogued the legislature and announced his resignation.

It was triggered by the government's initial reluctance to release all correspondence on the two projects, which it was eventually forced to do by a Speaker's order. Even though 56,000 pages of documents were made public, both opposition parties are convinced the government still has not released all the relevant information.