A Tory MP who serves as the prime minister's point-person on allegations of fraudulent calls to voters during the last federal election says his party doesn't know whether a former staffer who resigned last week had anything to do with the so-called "robocalls."

The Conservatives accepted the resignation of Michael Sona amid reports that Elections Canada was investigating allegations of robocalls misleading voters about polling station changes in the riding of Guelph leading up to last May's election.

In an interview airing Saturday on CBC Radio's The House, MP Dean Del Mastro was asked point blank if Sona was involved, and said "we don't know that."

Tory MP Dean Del Mastro says 'there seems to be an awful lot of evidence' that people in the Ontario riding of Guelph received misleading calls during the last election, but adds his party doesn't know who was responsible. (Adrian Wyld/Canadian Press)

Del Mastro again denied accusations from opposition parties that his party engaged in a voter suppression campaign, but told host Evan Solomon it appears that "what went wrong in Guelph was in fact untoward, it was intentional."

"The allegations of what happened there [in Guelph] are serious. There seems to be an awful lot of evidence that people received these misleading calls," said Del Mastro.

"We don't know what happened in Guelph. We don't have any information about what happened in Guelph. But what we can say is that the allegations that have come forward and the evidence that we've seen which is all public — we have no more information than anyone else on this — is troubling."

Del Mastro's comments about Sona contradict remarks made by a Conservative minister two days after the aide's resignation.

In an interview with CBC News last Sunday, Defence Minister Peter Mackay said: "I think they have identified the individual involved in this."

Sona, a staffer who worked in the office of Conservative MP Eve Adams until Feb. 24, also worked for Conservative candidate Marty Burke in the riding of Guelph during the last campaign.

A few days after Mackay's comments, Sona said he had quit because rumours that he was involved with the robocalls were preventing him from doing his job as a staffer, but added that he hoped the "real guilty party" would be apprehended.

To date, there has been no public evidence to show that he was involved with the robocalls.

According to Brad Lavigne, principal secretary to the leader of the Official Opposition, it is "highly unlikely" that this was the work of one individual.

Also in an interview airing Saturday on CBC radio's The House, Lavigne said "somebody would have to go postal code by postal code to find out where it would be in the interest of one political party to suppress the votes of their opponents."

"That would take time, and some expertise," said Lavigne.

Lavigne, who worked as the national campaign director for the NDP in the 2011 election, added that it is also "highly unlikely" that a national campaign would not be aware of the rogue actions of any campaign worker.

"There are checks and balances," Lavigne said.

Elections Canada confirms 'robocall' investigation

Conservatives counterattacked opposition claims of robocalls and other voter suppression tactics by calling it "a smear campaign."

But on Friday, Elections Canada confirmed it is investigating complaints regarding robocalls made in the last election.

"The agency has received 31,000 contacts," said a statement by John Enright, spokesman for Elections Canada. That includes contacts made by phone calls, email or snail mail.

Del Mastro told The House host Solomon that the party is not suggesting that the complaints from Canadians have "anything to do" with a "smear campaign" against the Conservative Party by opposition MPs.

"We're saying that the comments made in the House of Commons and elsewhere, by opposition members that have absolutely no evidence to support what they are saying, is in fact an unsubstantiated smear campaign," he said.

CBC News has learned that Astrid Dimond from Mission, B.C., is one of the many Canadians who made contact with Elections Canada prior to election day.

Dimond filed a complaint with Elections Canada in the days leading up to the May 2 election, about receiving phone calls from the Conservatives telling her to go to the wrong polling station.

When informed of Dimond's complaint, Del Mastro conceded that mistakes do happen in calls to people the Conservative Party has identified as supporters and is calling them to remind them to get out and vote.

"It's entirely possible that she did get that call from us, because we called an awful lot of people. And it's entirely possible that we may have been mistaken and provided her the wrong location," the Tory MP said.

"I guarantee you my campaign was not perfect. I guarantee you that if people called in to ask us where we vote and if we in fact disseminated that information, we would have been right almost all the time. But we would not have been right all the time."

In an email response dated May 3, 2011, the Office of the Commissioner of Canada Elections told Dimond "nothing prevents you from hanging up on any caller."

The response went on to say, Dimond could register her number with the Conservative Party's "Do Not Call" service, even pointed her to the CRTC for more information.

"Political campaign calls are a form of telemarketing, regulated by the Canadian Radio-Television Telecommunications Commission," said the email reply, which went on to suggest Dimond could also file a complaint through the national Do Not Call List.

Finally, the Office of the Commissioner of Canada Elections concluded by assuring Dimond that her complaint would be "considered in context with a broader inquiry ongoing with regard to irritating calls that occurred during this general election campaign."

Elections Canada said it will report all of its findings to Parliament.