"We didn't release our analysis immediately because, frankly, we were a little bit shocked by the conclusions," Matthew Bramley of the Pembina Institute commented.
Bramley and the Pembina Institute is calling on Environment Minister Jim Prentice to publish a fully transparent analysis of the proposed regulations before they are finalized in the fall.
In May, Prentice said Ottawa expects to release draft regulations this autumn that will spell out the requirements for heavy-duty vehicles and engines, starting between the 2014 and 2018 model years.
That followed an earlier agreement between Canada and the United States on common rules governing greenhouse gas emissions from cars and light trucks.
At the time, automakers praised the plans, which to Bramley, suggested "a bit of a hint that the industry got pretty much what it wanted in the regulations."
By 2016, the government projects the new measures will cut greenhouse gas emissions from vehicles by about 25 percent from those sold in 2008. Transportation accounts for about one-quarter of Canada's total greenhouse gas emissions.
The North American auto industry is highly interlinked, and Canada has said its strategy for emissions also hinges on U.S. policy because of the two nations' integrated economies.
Prentice has previously said the two countries will "effectively share common standards" for limiting vehicle greenhouse gas emissions. A spokesman for the minister was not immediately available for comment on Thursday.
Pembina's Bramley said Ottawa should not follow the U.S. lead because Canadians will not only lose the advantage of lower gasoline bills, it means the country will be making less progress environmentally than the United States.
Canada is frequently criticized by concerned groups across sectors for not doing enough to protect the environment and for allowing emissions of greenhouse gases to rise steadily over the last two decades.
Check out Pembina's climate blog for a more detailed analysis of the loopholes