Canada Supreme Court overturns one-vote election win in Quebec

Canada's top court has nullified a one-vote electoral win in Quebec, leaving the seat vacant until a byelection is called.

The closely-contested federal election last April in the electoral district, or riding, of Terrebonne, was initially declared for the Bloc Québécois, but a later recount found the Liberal party had won the seat by one vote.

The top court's ruling cancels the victory of 25-year-old Tatiana Auguste, a Liberal who won against Bloc member Nathalie Sinclair-Desgagné and has been sitting in Parliament ever since.

Politically, the ruling further complicates the arithmetic for Prime Minister Mark Carney. His Liberals now sit three seats short of a majority in the House of Commons.

The court ruled that the seat will now be vacant until a byelection is called, where the two candidates will face off once again.

Sinclair-Desgagné called for a do-over last year after Canadian media reported a Bloc voter's mail-in ballot was returned because of a misprint in a postal code on the return envelope.

Auguste's team argued that classifying a clerical error as an election irregularity did not set a good precedent - and in October a lower court agreed, ruling that the mis-print amounted to "human error" and was not grounds to overturn the election.

The Supreme Court disagreed on Friday nullifying the election results.

Last year, it looked like Carney's Liberals were closing in on a majority.

But that now seems increasingly out of reach, as Terrebonne is a highly-contested district.

Before Auguste's brief tenure, it had been held by the Bloc for decades.