An offshore wind farm developer that is in the midst of a lawsuit against the province of Ontario is now accusing the Liberal government of destroying documents related to its case.

In a notice of motion filed with the Ontario Superior Court, Trillium Power Wind Corp. says: "It has become apparent … that documents have been destroyed and records of communications have been wiped clean or deleted from computers, or assigned a code name to render their retrieval impossible."

Trillium spent years and millions of dollars developing plans for an offshore wind farm in Lake Ontario near Kingston, but it had the rug pulled out from under it in February, 2011, when the province said it would not consider any offshore development until more scientific studies were done. The decision came the same day Trillium was to sign a large financing deal.

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Trillium sued the government – initially for $2.25-billion in damages – but most of the grounds for the suit were thrown out of court.

However, in 2013 the Ontario Court of Appeal said the company could go ahead with one specific allegation, that the government's decision amounted to "malfeasance in public office."

As the revised suit – which reduced the claim for damages to $500-million – wound through the discovery process, Trillium found that some government documents it expected to see were not handed over.

Now the company has filed a notice of motion asking that its claim be amended to include the allegation of "spoliation," or the "deliberate destruction or elimination of incriminating evidence." None of these allegations, or the claims in the broader suit, have been proven in court.

Ontario's Liberal government has been hit with accusations that staff members under former premier Dalton McGuinty deleted documents related to the cancellation of two gas-fired power plants. Police are investigating the destruction of e-mails and other records.

The Trillium court filing alleges that the destruction and concealment of documents related to its case were done "concurrently with, and by the same persons" in the office of Mr. McGuinty and the cabinet office who deleted files in the gas plant case.

Jennifer Beaudry, a spokeswoman for Ontario Energy Minister Bob Chiarelli, said it is inappropriate for the minister to comment on the Trillium allegations because the case is before the courts.

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However, she said, "we take our record-keeping obligations very seriously. We're committed to being open, accountable and transparent." The government has implemented "significant record-keeping reforms" including mandatory staff training and new legislation that implements recommendations of the Privacy Commissioner, she said.

Trillium's lawyer Morris Cooper said his client's claim is that "the energy brief was destroyed" pretty much in its entirety when the gas plant files were erased. "All of the communications from the cabinet office and the office of the premier are gone. And there are e-mails confirming an intention to purge, and e-mails confirming an instruction to alter the offshore file to a codeword," he said.

Among Trillium's evidence for the destruction of documents, its court filing says, is that some of the communications the company had with the government are "nowhere to be found in the [government's] documentary productions."

Trillium also said that the government has not produced any documents regarding internal discussions in the premier's office or the cabinet about cancelling offshore wind projects, even though it has said that decision was a "core policy decision" of the government.

The provincial government has denied any wrongdoing. A trial in the case is not likely before late in the summer, at the earliest.