The International Centre for Trade and Sustainable Development says a WTO preliminary report has found that Ontario's feed-in-tariff system is discriminatory against foreign suppliers of equipment for renewable energy generating facilities.
The feed-in-tariff system — established in 2009 — requires participating electricity generators in Ontario to source up to 60 per cent of their equipment in the province if they want to be eligible for subsidies.
Japan filed a WTO complaint against the Ontario government two years ago, arguing that the requirement amounted to "illegal subsidies" for Ontario companies.
The European Union, who joined in on the complaint last year, added that the scheme goes against the international WTO provisions.
According to the Geneva-based group, the WTO is expected to make the decision public in November.
"It is our view that the feed-in-tariff program is consistent with Canada's WTO obligations," a spokeswoman for Ontario's Ministry of Energy said Tuesday.
"Should the panel disagree, we are ready to pursue all options with the federal government, including an appeal of the decision," Georgina Kourakos said in an email.