Ontario's former premier sought the advice of a retired Canadian Supreme Court judge on derailing an opposition-led inquiry into his government's costly cancellation of two gas-fired power plants.

The legal opinion from the former judge is among the extraordinary efforts made by Dalton McGuinty to shield his government from scrutiny over the escalating scandal.

The judge's involvement followed attempts to pressure the Speaker of the legislature into changing his mind on a gas-plant ruling, recently released e-mails reveal. The e-mails added fresh fuel to the controversy just as the minority Liberals, under Mr. McGuinty's successor Kathleen Wynne, go to the polls this week in five by-elections. Mr. McGuinty paid a surprise visit to the campaign in his former Ottawa South riding Monday evening, said a Liberal official.

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David Livingston, Mr. McGuinty's former chief of staff, asked retired Supreme Court of Canada judge Ian Binnie last fall whether the government could sue the opposition for defamation and also order a judicial review into the Speaker's ruling.

Mr. Binnie advised that neither a defamation lawsuit or an inquiry by the courts would produce a "positive outcome," according to a copy of his 12-page opinion obtained by The Globe and Mail.

The high cost of scrapping the projects – $585-million at last count – is at the heart of opposition accusations that the government abandoned plans to build the electricity plants in Oakville and Mississauga to save Liberal seats during the 2011 provincial election.

Mr. Binnie says in his decision last Nov. 29 that a defamation action would do the government more harm than good and turn it into a "media circus."

Mr. Binnie also says he does not believe the government has grounds to seek a judicial review of Speaker Dave Levac's ruling involving the production of gas-plant documents, despite the "shrill tone and abusive language" of opposition members.

If MPPs "could run off to the courts with complaints about how a Speaker is exercising his power … the business of the house would grind to a halt," he says.

Mr. Livingston turned to Mr. Binnie after advisers to Mr. McGuinty failed to pressure the Speaker into changing his mind.

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Mr. Levac, a Liberal MPP, ruled last September that there is evidence then-energy minister Chris Bentley breached his privileges by refusing to release the gas-plant documents to a legislative committee four months earlier. The ruling left Mr. Bentley facing a rare contempt of Parliament censure.

"Speaker needs to follow up on his prima facie finding and change his mind," Don Guy, a former chief of staff to Mr. McGuinty who managed all three of his successful election campaigns, wrote in an e-mail dated Sept. 21.

Laura Miller, Mr. McGuinty's then-deputy chief of staff, responded that same day that Dave Gene, another staffer, "is putting [the Speaker] on notice that we need better here."

But the following day, Ms. Miller wrote another e-mail, saying Mr. Gene "isn't confident coming out of his chat w Levac."

Progressive Conservative MPP Lisa MacLeod accused the Liberals on Monday of attempting to "hijack" the democratic process. New Democratic MPP Gilles Bisson said the former premier's advisers tried to "bully" the Speaker.

Mr. Levac, for his part, could not be reached for comment. Mr. Guy and Ms. Miller both said on Monday that they felt compelled to bring the Tories' "unjust behaviour" to the Speaker's attention.

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Mr. Guy had no contact with the Speaker, he said in an e-mail to The Globe. But he said he advised staff in Mr. McGuinty's office that the only way to block the Tories from pursuing a contempt motion against Mr. Bentley, regardless of whether documents were released, was to get the Speaker to change his ruling.

"Otherwise," he said, "we were headed for a tragic and costly outcome due to the partisan witch hunt of the Opposition parties."

With reports from Adrian Morrow and Adam Radwanski