The NDP issued a statement Tuesday suggesting the emails could be part of a politically motivated dirty tricks campaign in advance of the Oct. 8 election.
The statement from party president David Wallbridge says the NDP received two threatening emails, one on Monday and a second on Tuesday. The party decided to lodge a complaint with police because the first email threatens an "unidentified action against the NDP," he said.
"The NDP is very concerned, not just about the possible threat in the emails, but by the fact that they contained anonymous and false allegations that were widely reported and tweeted by mainstream media," the statement says. "This gives a clear appearance that the email may have been a politically motivated dirty campaign trick."
The first email to the NDP accused the party of dominating and manipulating political discussions on Twitter and other social media websites by using automated accounts and paid staff to spread misinformation. The party has denied using such tactics.
The emails purport to come from Anonymous, a loosely organized online hacking group. One email said the party had 72 hours to stop the alleged tactics or "additional information will be released."
In his statement, the NDP's Wallbridge said one published report made a connection between the emails and a Liberal campaign worker, who has denied responsibility. As a result, the NDP called on Liberal Leader Stephen McNeil to determine whether any member of his campaign team is involved.
A spokesman for the Liberals said they have looked into the allegations.
"We've investigated and we feel comfortable and confident that no one involved in the campaign was involved in what happened," Kyley Harris said in an interview.
"The NDP, obviously, have felt threatened by this. The fact that they took it to police is probably the right move."