The papers emerged after a freedom of information request to see EU documents related to tar sands – also known as oil sands – was lodged by Transport and Environment, an environmental organisation.

But the documents were only released in heavily censored form by the EU Ombudsman P. Nikiforos Diamandouros because full disclosure “would seriously affect the current trade negotiations and Canada’s relations with the EU,” Diamandouros said in a statement.

Negotiations between Ottawa and Brussels on an EU-Canada Comprehensive Economic and Trade Agreement worth as much as $20 billion have been ongoing since 2009.