In a statement Monday, Trillium Power Wind Corp. said the Superior Court of Justice has allowed the new allegation in an amended $500-million statement of claim.
Trillium's unproven claim now includes allegations the Ontario government "intentionally destroyed evidence relevant to the central issue in this litigation and purged emails, records and documents from its files."
The suit arose in 2011 after the province cancelled the company's wind project in Lake Ontario, about 28 kilometres from Kingston, Ont. At the time, the government said more scientific studies were needed and issued a moratorium on offshore wind farms.
The company alleges the government cannot back its claim — through documents or communications — that the decision to cancel the project was a "core policy" decision.
In its statement of claim, Trillium asserts that government workers assigned a code name in discussions of the wind project to hide communications it says were designed to injure the company.
Trillium also says it found emails to and from the premier's office that are not listed in records the government produced as part of the litigation process.
"We were shocked to recently find proof that there was a wilful destruction of evidence more than one year after Trillium Power sued the government of Ontario," CEO John Kourtoff said in a statement.
"We strongly believe that this is both an attack on the administration of justice and on our carefully balanced evidentiary-based legal system."
None of Trillium's allegations has been proven in court.
Jennifer Beaudry, a spokeswoman for Energy Minister Bob Chiarelli, said the government couldn't comment on the ongoing litigation.
"We take our record-keeping obligations very seriously," Beaudry said in an email. "We're committed to being open, accountable and transparent."
The government said Monday it is still examining offshore wind farms.
"We're taking a cautious and responsible approach to offshore wind to allow for the development of scientific research and co-ordination," Beaudry said. "That’s why there is currently a moratorium."
This is not the first time the Liberal government has been accused of destroying sensitive documents — possibly illegally.
Provincial police are continuing to investigate deleted emails about then-premier Dalton McGuinty's cancellation of two gas-fired power plants in Mississauga and Oakville in the run-up to the 2011 election. Police allege the deletion took place in the final day's of McGuinty's government.
A Trillium lawyer said the case could go to trial in early 2016 but Kourtoff called on Premier Kathleen Wynne to resolve the litigation.
"What has been perpetrated here is an affront to the sensibilities of all Ontarians," he said.
"(Wynne) has to decide if she wants to resolve this matter, which is a litmus test for Canadian and international investors as well as for the rule of law."