The company, based in the US, was awarded damages by a tribunal appointed under the North American Free Trade Agreement (NAFTA) in a September decision that set a 30-day payment deadline.
"The Canadian government's failure to pay the award granted to Windstream by the NAFTA tribunal is unprecedented," said Windstream director David Mars. "Throughout the process, we have negotiated in good faith in order to reach a fair and reasonable solution, but it has become apparent that the Canadian government has shown complete disregard for its NAFTA obligations."
Windstream’s complaint was with Ontario, but under the NAFTA process it is the federal government that is held responsible for treaty violations.
Global Affairs Canada, which manages the country's diplomatic relations, said the government is in discussions with the province, according to reports in the Globe and Mail newspaper.
"Canada stands by its international commitments and fully intends to honour the tribunal's award in the case," it stated in an email response to the paper. "Steps are currently being taken to process the payment."