The Ontario Progressive Conservative Party has one-third fewer members than former leader Patrick Brown had claimed and, in the runup to a leadership race, its ranks could shrink even further once a probe into every name and address on the membership list is complete.

Mr. Brown announced at the PC Party's convention last November that the membership ranks had swelled from 10,000 to 200,000 during his 2.5 years at the helm.

In fact, the database contains 132,644 names, including 4,901 memberships sold online since Mr. Brown resigned, Interim Leader Vic Fedeli said in a statement on Saturday.

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He added the caveat that the tally might not be "completely accurate" and could change once his office completes its probe into every name and address in the database.

Questions around the accuracy of the membership list – which forms the foundation of any political party – come 34 days before the Tories choose a successor to Mr. Brown in one of the shortest leadership campaigns in Canadian history.

In addition to the names in the database, Mr. Fedeli said in the statement that officials made two discoveries: several boxes of unprocessed paper membership applications at PC Party headquarters totalling 9,671; and an additional 10,520 memberships that had not been uploaded to the database because "complete payment" had not been received. Most of these memberships were from contested ridings with "active" local nomination campaigns.

It is not known whether any of these members voted in nomination campaigns. Officials in Mr. Fedeli's office declined to respond to questions on Sunday.

Party insiders and activists said issues about the membership base lend legitimacy to would-be PC nominees and local officials in as many as 14 ridings across Ontario, who complained about broken rules and ballot-stuffing at nominations.

Tory MPP Randy Hillier said the discovery of the 10,520 memberships submitted to the party in bulk on an Excel spreadsheet without the accompanying membership forms or proof of payment raises serious concerns.

"Any way you look at it, the 200,000 number was wildly out of whack with reality and then we have these other considerations of just how memberships were being accepted," Mr. Hillier said in an interview.

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Jim Karahalios, a dissident conservative activist and a Cambridge, Ont., corporate lawyer who had been an outspoken critic of Mr. Brown's leadership, said the lack of supporting documents for the memberships on the Excel spreadsheet raise questions about the party's accounting procedures and why memberships were accepted without payment of the $10 fee. Mr. Karahalios wondered whether someone else could be paying the fee on behalf of people who didn't even know they were signed up as party members.

"Vic is doing great work," he said of the Interim Leader. "What he has uncovered on the membership is an example of how much things stink."

Mr. Fedeli announced the probe into the membership list last Tuesday, the same day he bowed out of the race to become permanent leader of the party, saying he needs to spend all of his time "rooting out the rot."

The controversy around the membership list comes as the leadership race for the PC Party gears up. Lawyer and businesswoman Caroline Mulroney will officially enter the race on Monday. She joins former veteran Tory MPP Christine Elliott and former Toronto councillor Doug Ford. Rod Phillips, the former head of newspaper chain Postmedia who had been mulling throwing his hat in the ring, announced on Sunday that he is bowing out and supporting Ms. Mulroney.

Mr. Brown abruptly resigned on Jan. 25, hours after a CTV News report alleged sexual misconduct involving two young women. He has denied the allegations and remains in caucus. Three days later, Ontario PC party president Rick Dykstra also resigned amid a sexual-assault allegation, which he denies.

Ms. Mulroney, a lawyer who studied at New York University and the daughter of former prime minister Brian Mulroney, was named as a PC candidate in the York-Simcoe riding last September. She was pegged early on as a leadership contender, though she has never held political office.

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"After 15 years of Liberal government we need a fresh change," Ms. Mulroney said on Sunday. "People are tired. They want a new government. They want something new. So, I decided to put my name forward."

Ms. Elliott, the widow of former federal Conservative finance minister Jim Flaherty, and a lawyer who has twice vied for the PC leadership, announced on Twitter last Thursday that she will join the race.

In the first rally of his campaign, Mr. Ford, brother of late Toronto mayor Rob Ford, said he will keep taxes low and bring back manufacturing jobs. "I will not support policies that increase taxes and make life more expensive for each and every one of you," he told cheering supporters in Toronto Saturday night.

Mr. Ford also said he would not implement a carbon tax in the province, should he win the leadership and oust the Liberals from office at the provincial election on June 7. "Folks," he said, "this is a bad tax."

The leadership rules say a contender must support the "aims, principles and objects of the party and the policy resolutions" adopted at a PC Party convention last November, which said the Tories will opt in on federal carbon-pricing benchmarks. But Mr. Karahalios, who heads a campaign called "Axe the Carbon Tax," said contenders are free to run against the carbon tax without breaking the rules.

Speaking to Ontario Liberal Party members during a convention this weekend, Premier Kathleen Wynne urged supporters to focus on the needs of Ontarians rather than political turmoil among opponents. "It's not about who we're fighting against," she said on Saturday. "It's about who we're fighting for."

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With a report from The Canadian Press