The Trudeau camp had requested the extension, arguing that the party needs more time to get registration packages to more than 100,000 supporters who signed up without providing their email addresses.
More than 60 per cent of those supporters were signed up by the Trudeau team.
Only those who register will be allowed to cast ballots during the week of April 6; so far only a third of the party's 294,000 members and supporters have done so.
The deadline for registration was supposed to be Thursday but the party has now granted Trudeau's request and extended it to March 21.
Joyce Murray's camp strenuously opposed an extension, but the Vancouver MP says she'll accept the party's decision.
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