Top officials in former premier Dalton McGuinty's office and the Ministry of Energy deleted emails on the cancellation of the gas plants in Oakville and Mississauga, Information and Privacy Commissioner Ann Cavoukian found after investigating an NDP complaint.
"It truly strains credulity to think that absolutely no records ... responsive to the Speaker's ruling were retained," Cavoukian wrote in her special report called "Deleting Accountability: Records Management Practices of Political Staff."
"It is difficult to accept that the routine deletion of emails was not in fact an attempt by staff ... to avoid transparency and accountability."
The Progressive Conservatives said the report is proof of an attempt by the Liberals to cover up the costs of cancelling the gas plants, estimated to be at least $585 million.
"Our suspicions have finally been confirmed," said PC critic Rob Leone.
"It is reprehensible that the premier's office purposely deleted emails to avoid the truth from being exposed about their involvement in the gas plant scandals."
NDP Leader Andrea Horwath said the commissioner's report shows "it's obviously not in the Liberals' DNA" to be transparent or accountable.
"Does the premier really believe that when the Minister of Energy's chief of staff, the former premier's chief of staff, his principal secretary and his energy adviser were destroying all of these documents, that they were simply trying to keep their inboxes clean?" Horwath asked during question period.
There are no penalties for the former Liberal staffers who deleted their gas plant records in violation of the Archives and Recordkeeping Act.
"Maybe we should be taking a look at penalty provisions," said Attorney General John Gerretsen, who admitted he wasn't sure of the rules on keeping emails.
"I'm quite sure that a lot of us would not have been totally familiar with what you can or cannot delete, quite frankly, from emails," said Gerretsen.
Premier Kathleen Wynne said she has made it clear since taking over from McGuinty that all staff are to be briefed on how to follow the rules on retention of documents.
"We have taken proactive steps since we've been here in February to make sure that all the rules are being followed and information is available and is retained and all of those protocols are in place," Wynne told the legislature.
The Liberals' initial reluctance to release documents on the gas plants requested by an opposition-dominated committee triggered a rare contempt of parliament motion last fall that ground legislative business to a halt.
McGuinty cited the bitter debate over the contempt motion as one of the reasons for proroguing the legislature when he announced his resignation as premier last October, just hours before public hearings into the gas plants were scheduled to begin.
Cavoukian found that as recently as January 2013, staff in McGuinty's office asked the secretary of cabinet, Ontario's top civil servant, how to permanently delete emails and other electronic documents from government databases.
"I was very concerned with the prospect of inappropriate deletions of electronic records by political staff in the former premier's office," she wrote.
Cavoukian singled out David Livingston, McGuinty's former chief of staff, and Craig MacLennan, the former chief of staff at the Ministry of Energy, for violating the Archives and Recordkeeping Act.
It's "quite frankly unbelievable" that any minister's political staff would think it appropriate to delete all email records on the gas plants, she said.
The NDP had complained to Cavoukian after documents they obtained through Freedom of Information requests showed there were no emails for several top McGuinty aides.
"This failure to comply with the records retention requirements, coupled with a culture of avoiding the creation of written and electronic records, assists in explaining the apparent paucity of documents relating to the gas plant closures produced by the offices of the former minister of energy and the former premier," she said.
Cavoukian recommended a review of the government's record retention policies, that staff be properly trained in their records management obligations and that a directive be issued to all staff in the premier's and ministers' offices regarding her report.
"Our government is committed to addressing the issues raised by the commissioner to ensure that situations as referred to in her report do not happen again," said Government Services Minister John Milloy.
Horwath was asked how the NDP could continue to support the minority government and agree to vote for the budget knowing that the Liberals had broken the law to try to cover up the cost of the gas plant cancellations.
"These are important things that we were able to achieve in that budget, and so we're proud of that work and we want it to stick for Ontarians," said Horwath.