If it's true that desperate times call for desperate measures, the Canadian government is acting like a junkie in need of a fix.

As public hearings on the proposed Northern Gateway tar sands pipeline proposal got underway in British Columbia last week, natural resources minister, Joe Oliver, lashed out at "environmental and other radical groups" and "jet-setting celebrities." In an open letter, he accused them of being the stooges of foreign special-interest groups, opposing tar sands development in order to undermine Canada's national economic interest.

The letter was so far off the mark, one can only conclude that the government is becoming unhinged over the growing opposition to tar sands development. This should be a cue for Britain to reconsider its unfailing support for Canada on this issue in the European context.

Why the desperation? Because in the midst of a protracted battle at home, Barack Obama's decision in November to send back to the drawing board another proposed pipeline – Keystone XL – came as an unexpected and unwelcome surprise. As a result, government and industry are tag teaming on an all-out public relations war – a war that they realise they could actually lose.

While Keystone would carry bitumen from Alberta to the Gulf of Mexico, Northern Gateway would carry it across the beautiful Great Bear rainforest to the marine port of Kitimat in British Columbia. From there, it would be transferred to supertankers for transport onward to Asia. Coastal communities, haunted by the spectre of the Exxon Valdez, are fighting to keep their waters free of tankers.

It's not just environmentalists opposing the project. Those "other radical groups," as Oliver dismissively referred to them, must be the more than 60 first nations (aboriginal bands) of British Columbia that have signed a declaration saying "we will not allow the proposed Enbridge Northern Gateway pipelines or other similar tar sands projects to cross our lands, territories and watersheds, or the ocean migration routes of Fraser River salmon."

This is significant because the government is obliged to consult and accommodate first nations on industrial projects that affect their traditional lands. Only one BC band, the Gitxsan, has come out in support of the pipeline. But it subsequently turned out that those doing the negotiating had acted beyond their authority and were fired.

As for Oliver's heartburn over "foreign special-interest groups" engaged in the tar sands fight, it's a peculiar accusation given the effort and money spent by Canadian companies and the government to influence decisions outside Canada.

TransCanada, the company behind Keystone, spent $1.5m on lobbyists to influence Washington, even more in states bordering the pipeline route, and an advertising campaign in Washington DC to boot. And Canadian government officials, including Oliver himself, are aggressively lobbying European countries (with considerable success in the UK) to overturn provisions of the EU fuel quality directive.

The directive uses scientific fact to classify fuels, and tar sands has been found to be an unconventional fuel with disproportionately high greenhouse gas emissions. This would put it at a disadvantage in the European energy market, hence the charm offensive.

Even more ironic, however, is that the tar sands projects themselves are being bought up at an astonishing rate by foreign investors, especially China which has purchased billions of dollars' worth of shares. As one journalist quipped: "if we're seriously supposed to be going all villagers-with-torches about foreign outfits with weird ideologies undermining Canada's national economic interests, let's review what's really going on."

The fact is that beyond the very real local risks of oil spills that Canadians are rightly studying, the global community has a stake in stopping the kinds of massive high-carbon infrastructure projects that the International Energy Agency (those radical foreigners!) warned against in its annual World Energy Outlook published last November. Britain claims to be a climate leader. And the European Union is playing a leading role among developed countries to bring CO 2 emissions under control, though it can and should be doing much more. The fuel quality directive is an important tool for getting to grips with high-carbon fuel sources, by bringing transparency and a proper accounting system to assess their relative impacts, which in turn will allow for better informed choice. It stands to reason that Britain should strongly support it.

Given Canada's lack of credibility on this issue – apart from this latest gaffe there have been a number of well-documented unsubstantiated claims – Britain's "greenest government ever" should stop doing Canada's bidding in Europe by seeking to weaken the fuel quality directive.

The next time Canada is in need of a fix, please David Cameron, just say no.

• Kelly Rigg is the head of TckTckTck, the coalition of more than 200 NGOs pushing for a strong global deal on climate change