A defamation lawsuit by Subway against Canada's public broadcaster over a report on the chain's chicken sandwiches can proceed, Ontario's top court has ruled.

In a statement of defence filed earlier this month, the broadcaster says it diligently conducted a "fair and thorough" investigation into several fast-food chicken products, including Subway's oven-roasted chicken and chicken strip items.

Subway has filed a lawsuit against the CBC over a report that claimed the sandwich chain's chicken products contain high levels of soy filler.