Secret documents on the cost of scrapping Oakville and Mississauga power plants — both in Liberal ridings — must be released, the Speaker of Ontario’s legislature ruled Thursday.

The decision has Energy Minister Chris Bentley on the verge of a rare contempt of parliament censure for refusing to release the documents ordered by a legislative committee in May.

While the $190-million cost of scrapping the Mississauga plant during last fall’s whisker-close provincial election has been known since July, opposition parties have been frustrated in getting a tab for Oakville.

The Progressive Conservatives and NDP charge the cancellations were part of a Liberal “seat saver” effort to keep the government alive.

“We need those documents to do our job,” said Conservative MPP Rob Leone (Cambridge), who made the motion for the papers to be releases.

“What are you hiding?” he shot at Bentley during a rough-and-tumble question period.

In slamming Bentley for defying parliamentary privilege, Speaker Dave Levac set a Sept. 24 deadline for the minority Liberal government and opposition parties to work out a deal on releasing the documents in some form.

“We will be complying with the ruling,” said Bentley, who had argued the papers were commercially sensitive and their release would violate solicitor-client privilege as negotiations continue on compensation for the builder of the cancelled Oakville plant.

“The position I’ve been in is to act in the best interests of Ontarians,” added Bentley.

Government House leader John Milloy said he wants a deal so the documents can be viewed by committee members without “damaging the position of the government of Ontario” in negotiations.

But only a full public release is acceptable because taxpayers are entitled to know details for the bill they’ll be paying, said NDP Leader Andrea Horwath.

“Once again, the Liberals are more concerned about their own political fortunes than they are about the taxpayers . . . we have every right, on behalf of the people, to get the information we need to hold the government to account.”

A vote on holding Bentley in contempt would be held — and likely pass, given that Liberals are a minority in the legislature — if documents are not produced to the opposition’s satisfaction.

There is no concrete penalty for contempt other than censure.

“Hopefully, they will suffer in the court of public opinion for being such rascals . . . that’s the ultimate censure of any government, what does the public think?” said Tory House leader Jim Wilson.