TORONTO -- The $585 million price tag for the Liberal government's decisions to scrap planned gas plants in Oakville and Mississauga is expected to soar even higher next Tuesday when Ontario's auditor general releases a second report into the cancellations.

The audit of the costs of cancelling the Oakville energy project and moving it to the Napanee area near Kingston will be introduced in the legislature Oct. 8, new auditor general Bonnie Lysyk said in a letter informing the parties her report was ready.

"It is my understanding that the Speaker will lay the report before the House around 3 p.m. on that day," wrote Lysyk.

The Liberals cancelled the Oakville gas plant, and another in neighbouring Mississauga, prior to the 2011 election in what the opposition parties called "an expensive Liberal seat saving program."

The New Democrats said they were looking forward to the auditor's report.

"The people stuck paying the tab for this cynical election strategy have been waiting a long time for answers," said NDP Leader Andrea Horwath. "For years, the Liberal government offered a series of evasions, dodges and figures that just weren't credible."

Former premier Dalton McGuinty -- who has said he was the one who made the decisions to cancel the two energy projects -- had said the Oakville decision would cost about $40 million, a figure that was later jumped up to $310 million by the Ontario Power Authority.

It's expected the cost of the Oakville project will come in even higher than the OPA's estimate.

Former auditor James McCarter warned his office would use the same criteria to estimate savings over the 20-year life of the electricity contract signed with the builders of the Napanee gas plant as it did on Mississauga.

McCarter found the Mississauga gas plant, which was halted in mid-construction two weeks before election day in Oct. 2011, cost $275 million, $85 million more than the government had been claiming.

Lysyk said she will hold a news conference when the report is released to discuss her findings.

A statement from Kathleen Wynne's office said the premier has made sure the opposition parties have been able to get as many documents on the cancelled gas plants as she can.

"We have provided the justice committee with more than 148,000 documents and emails related to the gas plants, including 30,000 directly from the premier's office," said Wynne's press secretary Zita Astravas.

The Liberals' initial refusal to release the gas plant documents led to a rare preliminary finding of contempt of parliament against then energy minister Chris Bentley. It led to a nasty, bitter and at times personal debate that tied up all other legislative business, and was cited by McGuinty last October as one of the reasons he prorogued the legislature and resigned as premier.

Construction had never started on the Oakville project, which faced widespread opposition from well-heeled local residents who brought in American environmentalist Erin Brockovich to speak against building a gas plant so close to homes, schools and a hospital. It was cancelled hours later.

However, the Liberals' mid-campaign decision to cancel the Mississauga gas plant did not stop construction on that project, which continued for almost two months past election day, when the Liberals saved their seats in the Oakville-Mississauga area but fell one seat short of a majority.

Wynne has apologized for the decisions and said they should have been done in a better way. McGuinty has never apologized, and said he cancelled the projects when he realized the residents were correct to not want a gas plant built close to their homes.