Kevin O'Leary's candid assertion that he is using private aircraft to campaign for the Conservative Party leadership while expensing only the price of a commercial ticket appears to be a violation of Elections Canada rules, opposition critics in Ottawa say.

But Mr. O'Leary's campaign team tried to walk back the Toronto businessman's description of his electioneering travel, saying the leadership candidate is in fact flying commercial aircraft to leadership events in the race for the helm of the federal Conservative Party.

"I would have to double-check with him on that [about what Mr. O'Leary said] but what I have been told from our team, that is not the case," campaign spokesman Ari Laskin said in an interview Tuesday. "We do not use private planes for the leadership campaign."

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In a later phone call, Mr. Laskin acknowledged there are times where the reality-TV-star-turned-Tory-contender travels to leadership events on a chartered Pilatus PC-12 turboprop plane while also on business for his O'Shares company.

In those instances, Mr. Laskin said Mr. O'Leary expenses the cost of a standard airline ticket for the travel to the campaign event so he can be in compliance with Elections Canada spending rules.

He would not say how many times Mr. O'Leary has used the chartered aircraft nor would he share the invoices related to this travel.

In a stark contrast to what his leadership team is saying, Mr. O'Leary told The Globe and Mail on Monday that he uses private aircraft when he has campaign appearances booked between various cities.

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"Yeah, I do use private planes as I do in business, but I can't charge that to the campaign. I can only charge the price of a ticket. Sometimes I have to be in four cities at once. Why wouldn't I use a private plane?" Mr. O'Leary said.

Once again on Tuesday, Mr. O'Leary – who is in full campaign mode – underlined how necessary it is for him to rent private planes for campaign travel.

"I make use of private planes all the time in business because I need to be sometimes in five cities in one day. That is exactly what is going on in this campaign," he told CTV News Channel. "I am jumping all over the place and occasionally I do use a private plane, but we are going by the rules."

Elections Canada said Tuesday a leadership candidate can only expense incremental costs if air travel overlaps with non-campaign activities.

Otherwise, Elections Canada spokesman John Enright said the "entire cost" of operating an aircraft must be expensed "if a private plane was used exclusively for the purpose of the leadership campaign."

Mr. Laskin first told The Globe that Elections Canada has told the O'Leary campaign "we are in full compliance" with the rules.

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"I can say any time he has used it [the private plane], it has been for O'Shares business. … Any time that he is using the plane and he happens to be going to a campaign event, what the campaign does – for us to be in compliance with the Elections Act – is we will cover the commercial equivalent of that flight and the rest of the costs come out of Mr. O'Leary's pocket."

Mr. Laskin later called back with another explanation for why Mr. O'Leary could not be in breach of the election laws.

"The rules are that if he is the only person on the plane, then it counts as personal expense. If there is campaign staff on the plane, then it counts as a campaign expense [but] we've never had campaign staff travel on charter," he said.

Elections Canada said it lays out the rules for campaign spending and does not issue approvals.

"Generally speaking, if a campaign were to consult us on a specific question, our response would be to remind them of the rules and requirements under the Canada Elections Act and they would be expected to govern themselves accordingly," Mr. Enright said.

NDP MP Ethics critic Nathan Cullen has called on Elections Canada to immediately investigate Mr. O'Leary's use of private aircraft. The business executive is coming under increased scrutiny as one of the perceived front-runners in the final months of the Conservative leadership contest.

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"Mr. O'Leary needs to be very clear about these flights as there are strict rules set out by Elections Canada. He needs to clearly state who is paying for these flights, who is travelling with him and if he is accurately reporting these expenses," Mr. Cullen said.

Liberal Party spokesman Braeden Caley joined in the criticism of Mr. O'Leary and suggested he was out of touch with Elections Canada rules because he lives a large part of the year in the United States, where he has homes in Boston and Florida.

"Not having spent much time in Canada lately, Kevin O'Leary may not be very aware of the clear rules we have in this country for campaign contributions and spending. The rules exist for a reason and they cannot be ignored just because a candidate says they are rich," Mr. Caley said. "We hope this matter will be appropriately reviewed by Elections Canada."

Conservative leadership hopeful Andrew Scheer mocked Mr. O'Leary for being out of touch with ordinary Canadians.

"I don't have a private plane. Our family is between Cessnas right now. The minivan is not going to get me between Canadian cities quickly so we're relying on the good people at WestJet and Air Canada these days," he said.

On Tuesday, Mr. O'Leary sat out a bilingual leadership debate in Edmonton attended by the rest of the 14 candidates in the race. Mr. O'Leary, citing his dissatisfaction with an all-candidates format, held his own gathering with party members, several blocks away.

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With a report from The Canadian Press