The federal NDP says it's aware of at least 34 ridings where voters received automated phone calls on election day, including one in Edmonton.

The opposition is accusing the Harper Conservatives of using dirty tricks in last year's federal election.

In Eastern Canada, Conservative party workers allegedly made automated phone calls while pretending to be officials from Elections Canada in order to confuse or anger supporters of rival parties.

NDP candidate Ray Martin recalled hearing of two such calls in his riding of Edmonton East in April 2011, but he didn't think much of it at the time, he said.

But now Martin believes the calls were part of a larger campaign.

"I've never seen what seems to be an organized approach across the country the way it was in this last election, borrowing sort of the (U.S.) Republican Party's sort of hardball politics."

"I'm very surprised," said his campaign manager John Ashton. "I've heard of voter-suppression tactics like this in the U.S., but...I can't believe here in Edmonton or in Canada."

Martin says it wasn't a factor in his campaign as he lost by 7,000 votes to then-Conservative Peter Goldring.

Elections Canada and police are investigating the reports of the so-called robo-calls.

Acting Liberal leader, Bob Rae, has demanded an emergency debate on the issue for later today.