The federal Conservative party removed more than 1,300 people from its membership rolls Friday following a review triggered by leadership hopeful Kevin O'Leary's accusation that one of his rivals has been engaging in widespread fraud and vote-rigging.

The party's announcement capped a day in which O'Leary's allegations were attacked or mocked by a number of his leadership rivals, most particularly by Maxime Bernier who bluntly dismissed the celebrity businessman as a sore loser.

Yet the party's findings backed up O'Leary's assertion, levelled late Thursday, that unnamed backroom organizers were trying to buy the leadership race by using untraceable, pre-paid credit cards to sign up fake members.

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After an expedited review, the party revealed Friday that it found 1,351 memberships were purchased through two IP addresses, not paid for by each individual as required under party rules. Those memberships have been cancelled and the individuals are no longer eligible to vote in the leadership contest.

Over the last six months, the party said it has received 1,233 pre-paid credit card transactions through its website, roughly half of which have been traced to the two IP addresses.

Party spokesman Cory Hann said it wasn't possible to determine which leadership campaign or campaigns were involved since the memberships were purchased anonymously through the party's website.

While O'Leary never pointed a finger at a specific campaign, sources had said the Bernier campaign was the alleged culprit.

Bernier fired back Friday, pulling no punches in a bluntly worded fundraising email to his supporters.

"Kevin O'Leary is a loser. I'm a winner," Bernier said.

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"He knows my campaign has raised more money, signed up more members, has more supporters and more volunteers. He's a bad candidate. Instead of trying to win people over by putting out a platform, he's throwing mud to try to save his campaign."

While he's been building "an army of supporters," Bernier said O'Leary has been "vacationing in Florida, filming in L.A. and shilling on a home shopping channel trying to sell his line of O'Leary wine to American buyers. It's not even available in Canada."

However, after the party announced it had found merit to O'Leary's complaint, Bernier took to Twitter to say: "Good news. Conservative Party membership review process is working properly."

O'Leary tweeted his satisfaction that "fraudulently purchased memberships" have been struck from the membership rolls.

"Pleased w/ the Party, we need to be sure we find them all," he said.

In a statement late Friday, O'Leary expressed concern that there will be many more fake memberships submitted before a Mar. 28 deadline to buy a membership in time to be eligible to vote for a new leader.

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"There are clearly forces at work who are trying to influence the outcome," the statement said.

Earlier Friday, O'Leary attempted to enlist the other candidates in his fight against what he called a scam concocted by "sketchy insiders." But some of his rivals seemed unsympathetic.

Andrew Saxton and Rick Peterson challenged O'Leary, who has participated in just two leadership debates, to participate in future debates if he's so concerned about promoting democracy.

Kellie Leitch suggested it's a bit rich for O'Leary "to cast aspersions on the other candidates in this race without a shred of evidence" when he's the only candidate who's been fined by the party — for refusing to attend a bilingual debate in Edmonton.

"You need to put up or shut up Kevin," she tweeted.

Brad Trost also called on O'Leary to provide proof of his allegations, immediately and publicly.

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"If this is nothing but a publicity stunt and Mr. O'Leary has no evidence, then he should be sanctioned to the greatest extent possible by the party," Trost said.

Memberships in the party cost $15 and party rules state they can only be purchased by personal credit card or cheque, a provision implemented specifically to avoid campaigns being able to use their own funds to sign up thousands of members, as had been the practice in the past.

The new system drew grumbling when it was unveiled, with some saying the fee — originally set at $25 — was still too high and the credit card process too cumbersome.

There are believed to currently be about 100,000 party members. The leadership vote is scheduled to take place in May.