TORONTO -- Progressive Conservative Leader Tim Hudak says Premier Dalton McGuinty "lied" to the legislature to "cover up" the true cost of cancelling power plants in Oakville and Mississauga.

Hudak told a news conference that Friday's dump of another 20,000 pages on the gas plants shows McGuinty and Energy Minister Chris Bentley were not truthful when they repeatedly insisted all relevant documents were released Sept. 24.

The Tories plan to raise the issue with the Speaker before question period, which could block the government from releasing its fall economic update later today.

The Liberals admit taxpayers will be on the hook for $230 million for scrapping the two gas plants, but the PCs and NDP put that figure at a minimum of $650 million.

Hudak says Bentley's claim that they honestly thought all documents had been released last month "doesn't pass the sniff test," and accuses the Liberals of an orchestrated cover up.

McGuinty was not immediately available for comment.

NDP Leader Andrea Horwath says it's clear "the government was not being honest" when it claimed to have released all the gas plant documents in September.

"There's no good reason to believe they've fully complied now," Horwath said in an email to The Canadian Press.

Hudak complained in a letter Sunday that the second batch of documents "is virtually missing any correspondence or briefing materials at the political level," the same complaint the opposition parties made about the first 36,000.

"We have no reason to believe that this latest package of documents is complete," wrote Hudak.

Friday's package is "almost devoid of emails, correspondence or briefing documents between the offices of the energy minister, premier or cabinet office," added the Opposition leader.

The fight by the Tories and NDP to get the documents from the Liberals triggered a contempt motion against Bentley that derailed all other legislative business for a week.

Despite an impassioned, last-minute plea from McGuinty the opposition parties out-voted the minority government to send the contempt motion, and the issue of the gas plant documents, to the Finance Committee, which is to begin hearings this week.

McGuinty "needs to take responsibility" for the scandal, and can start by agreeing to testify before the committee "to explain his role in this mess," said Horwath.