The Council of Canadians and the Canadian Federation of Students have filed evidence to support a constitutional challenge of last year's legislation, dubbed the Fair Elections Act by the Harper government.
"The very legitimacy of the government is at issue if these rules stand, in our submission," lawyer Steven Shrybman told a news conference Monday.
The groups say new voter identification rules contravene Section 3 of the charter, which states everyone has the right to vote, as well as the equality provisions in the Constitution.
The office of Democratic Reform Minister Pierre Poilievre did not respond to a request for comment on the court challenge.
The Fair Elections Act was introduced last February to near-universal condemnation from electoral experts from across Canada and abroad, and the Conservatives eventually removed a number of the most contentious aspects of the bill before rushing it through the House of Commons and the Senate.
However the new rules still forbid voters from using the Elections Canada voter identification card mailed to their home as proof of residency — although some 400,000 voters used the cards for this purpose in the 2011 federal election.
The law also now sets up a more restrictive process for attesting to the identity of voters who don't have proper identification — a process known as vouching, which allowed 120,000 additional voters to cast a ballot in 2011.
"The most fundamental right in a democratic society is the right to vote in elections that are free and fair," said Gary Neal of the left-leading Council of Canadians.
Jessica McCormick of the student federation said thousands of post-secondary students looking to vote for the first time this year will be shut out by the new rules requiring ID with a local address.
With a fixed federal election date set for mid-October, time is quickly running out for the legal challenge. A court date has yet to be set to hear the case, said Shrybman.
The groups will seek a court injunction setting aside the new election rules if the case can't be heard before Canadians go to the polls.
Shrybman noted that fewer than 10,000 votes spread across 16 close ridings were the difference between a Conservative majority and minority in the last election.
"Remember that a few hundred votes, a few dozen votes — certainly a few thousand votes — can determine the outcome of an election in any riding," said Shrybman.
Follow @bcheadle on Twitter