Canada's carbon emissions will soar 38% by 2030 mainly due to expanding tar sands projects, according to the government's own projections.

In a new report (pdf) to the United Nations, the Harper administration says it expects emissions of 815million tonnes of CO2 in 2030, up from 590Mt in 1990. Emissions from the fast-growing tar sands sector is projected to quadruple between 2005 and 2030, reaching 137Mt a year, more than Belgium and many other countries, the report shows.

Worse, Canada is likely under-reporting its emissions. An investigation in 2013 found that Canada's reported emissions from its natural gas sector, the world's third largest, could be missing as much as 212Mt in 2011 alone.

"Canada appears to have vastly underestimated fugitive emissions (leaks) from gas exploration," possibly because of "inadequate accounting methodology " according to the Climate Action Tracker analysis done by Germany's Climate Analytics, the Potsdam Institute for Climate Impact Research and Dutch-based energy institute Ecofys.

Bill McKibben, founder of the grassroots climate campaigning organisation 350.org, told the Guardian: "Who'd have imagined that digging up the tar sands would somehow add carbon to the atmosphere? That Canada watched the Arctic melt and then responded like this will be remembered by history."

The Harper government pulled out of the Kyoto Protocol in 2011, promising instead to meet a weaker target of cutting emissions 17% by 2020, against 2005 levels. But an Environment Canada report last autumn revealed emissions would likely be 20% higher in 2020, leading environment minister, Leona Aglukaq, to say "we're getting results" when asked about the likely gap.

The EU, by contrast, is considering carbon cuts of around 40% by 2030.

The Canadian government has never attempted to implement the policies or slow the rapid expansion of the tar sands that could have enabled Canada to meet its 2020 target, said Mark Jaccard, an energy economist at Canada's Simon Frasier University and former Harper government appointee.

"Now it's too late. The government is not telling the truth to Canadians about the climate impacts of its energy policies," Jaccard told the Guardian. "We in Canada are living an Orwellian nightmare when it comes to our government and climate."

It is "simply irresponsible for a country like Canada, given the impacts of climate change that are already taking place," to increase its emissions or even maintain them, said Canadian scientist Corinne Le Quéré of the Tyndall Centre for Climate Change Research and co-chair of the Global Carbon Project.

Canada has become an "outcast amongst its negotiating peers " at recent UN climate summits, said Liz Gallagher head of the Climate Diplomacy Programme at E3G, a UK-based NGO.

"It’s a travesty that a prosperous country with such a rich history of international cooperation is now turning its back on the world," she said.