Premier Kathleen Wynne says she played no role in decisions to cancel power plants in Oakville and Mississauga before the 2011 election — moves now costing Ontarians $585 million on their tax and hydro bills.

The new tab in a scandal dominating provincial politics came Tuesday as Ontario Power Authority (OPA) chief executive Colin Andersen revealed a bombshell: the latest tab for scrapping Oakville is $310 million, on top of $275 million for Mississauga.

That Oakville cost is almost eight times higher than the $40 million the minority Liberal government has long claimed.

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“That number has changed and I’m frustrated about that,” the premier said amid testy exchanges with opposition MPPs in a legislative committee investigating the cancellations, which the premier has acknowledged were “politically motivated .”

Wynne was repeatedly asked when she knew the figure was higher than $40 million.

The premier said she didn’t learn a different number until a March 20 memo from the OPA putting the costs for Oakville at between $33 million and $136 million. By Tuesday, that had risen to $310 million.

Wynne, who took over from Dalton McGuinty in February, denied charges she misled the province on the true costs of the Oakville cancellation.

“Whenever I have stood and used a number, that has been the number that I have understood to be the real number,” she testified, adding she has tried to avoid using any Oakville figure in the last several weeks.

“The fact the OPA numbers keep changing justifies my decision to call in the auditor,” Wynne said, referring to an auditor general’s report on Oakville costs due by September.

Both power plants were in Liberal ridings and faced community opposition heading into the Oct. 6, 2011 election that saw McGuinty’s Liberals reduced to a minority.

Opposition MPPs said Wynne was “evasive” in her testimony.

“She knows her government’s been lying all along,” charged Progressive Conservative MPP and energy critic Vic Fedeli (Nipissing).

New Democrat Taras Natyshak (Essex) said he found it “hard to believe” Wynne, who was vice-chair of the Liberals’ 2011 re-election campaign, didn’t know of the Mississauga cancellation in advance.

“I learned of the campaign commitment from media reports,” Wynne testified.

The $310 million Oakville figure from the OPA’s Andersen was the second blow to the government in as many weeks on power plant cancellation costs.

Auditor general Jim McCarter released a report saying the costs to cancel the Mississauga plant and move it to Sarnia are $275 million — 45 per cent higher than the government claimed. Jim McCarter released a report saying the costs to cancel the Mississauga plant and move it to Sarnia are $275 million — 45 per cent higher than the government claimed.

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Andersen said “everybody, including the (energy) minister” knew the number was going to be higher than the $40 million in so-called “sunk costs” that were spent on developing the Oakville plant site and could not be recovered after it was scrapped in October 2010.

“We all knew that those were going to be there and they were going to be significant,” Andersen added.

In her testimony and earlier in the legislature’s question period, Wynne repeatedly noted the Liberals weren’t the only party promising to scrap the power plants.

“I regret this situation has come to this . . . every party in this house said they wanted these cancellations to happen,” the premier chided her political opponents.

Other estimates of cancelling the Oakville plant have been higher, in the range of $600 million.

Andersen told the committee the Oakville cost estimate will “continue to evolve” as additional information becomes available.

“To some extent, it’s like a Polaroid picture that takes 20 years to develop,” he added, a reference to 20 power-supply contracts given for power plants build for the province by private companies.

In the legislature, the Conservatives used Andersen’s revelation on Oakville to urge the New Democrats to help them defeat the government.

NDP Leader Andrea Horwath said she’s waiting to see what’s in the provincial budget Thursday — in which the New Democrats have made several demands — before making a final decision.

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