Stephen Harper has turned on the man once considered his most valuable aide, accusing Nigel Wright of deceiving him as the Prime Minister tries to contain political damage from the Senate expenses scandal ahead of a Conservative party convention.

The Conservative Prime Minister, struggling to deal with new allegations in the controversy, harshly condemned Mr. Wright's covert $90,000 gift to beleaguered Senator Mike Duffy while speaking to MPs in the Commons Tuesday.

"On our side there is one person responsible for this deception and that person is Mr. Wright. It is Mr. Wright by his own admission," the Prime Minister told Question Period.

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It was the toughest language the Conservative Leader has used to date to characterize Mr. Wright's conduct – and effectively a disavowal of a man who was long judged a strong and capable PMO chief of staff. Mr. Wright was lauded during his tenure for bringing Bay Street smarts to the Prime Minister's Office and putting on hold a lucrative business career for the public service.

The sharp shift in tone comes only days after Mr. Harper publicly revised his description of how Mr. Wright exited his office in May, telling a Halifax radio show Monday the aide was in fact "dismissed" when he'd previously described the departure as a resignation.

Mr. Wright remains based in Ottawa these days as he awaits the outcome of an RCMP investigation into the expenses scandal.

His lawyer did not immediately respond to a request for comment.

Mr. Harper has his eye on the clock this week as his government rushes to impose sanctions on three ex-Conservative senators accused of padding their expense accounts.

The Tories in the Senate are scrambling to suspend without pay Mr. Duffy, Pamela Wallin and Patrick Brazeau from the Red Chamber by Friday, when Mr. Harper must attend his party's convention in Calgary to address rank-and-file Conservatives – a group party insiders say is dispirited and frustrated by the scandal.

The Tory caucus in the Senate tabled a motion on Tuesday that would limit debate on the proposed suspensions and hasten a vote.

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If that motion is passed, the earliest the Conservatives will be able to force a vote on the suspensions would be this Friday – just as Mr. Harper prepares to give a keynote speech that aims to rebuild relations with the Tory faithful whom he will rely upon to win the 2015 federal election.

Grassroots Tories are angry at the Senate scandal because they see it as a betrayal of the Conservative Party's values. A predecessor party, the Reform Party, held overhauling the Senate as a key article of faith.

Unlike conservative predecessors such as Brian Mulroney – known for his loyalty – Mr. Harper has demonstrated a tendency to fairly quickly sever ties with those whose political blunders threaten his own reputation.

One former PMO insider, speaking on condition of anonymity, said that Mr. Harper initially demonstrated an unusual degree of loyalty to Mr. Wright, standing by his chief of staff for more than four days after the story first broke in May. At the time a PMO spokesman assured reporters that the Prime Minister had full confidence in his top aide.

The source says Mr. Harper did this despite the fact several federal cabinet ministers were calling for Mr. Wright to be turfed. "He stayed by Nigel a lot longer than he stayed by others," the source said.

Even as Mr. Wright left his office, the Prime Minister lauded his former aide publicly, saying he accepted the resignation "with great regret" and thanking him for his "tremendous contribution" to the government.

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As the scandal wears on, Mr. Harper is trying to contain the political damage from spreading beyond Mr. Wright.

News reports allege that as many as 13 Conservative insiders had some knowledge of the Duffy bailout, but Mr. Harper seems determined to beat back this characterization. He has insisted that "very few" knew.

The expense scandal once again dominated Question Period and the public gallery was packed with onlookers as NDP Leader Thomas Mulcair asked 26 questions on matter, grilling his Conservative rival.

The Prime Minister played down Mr. Duffy's new revelation that the Conservative Party dipped into its pool of donations to fund the PEI politician's legal bills, saying it's standard practice for the Tories to reimburse legal expense for members of their caucus.

Mr. Duffy had also alleged Monday that the Prime Minister's Office coached the senator to lie to Canadians about how he obtained $90,000 to pay back questionable expense claims.

The money was a gift from Mr. Wright, a millionaire businessman, but the PEI senator alleges he was ordered to tell the public he had taken a loan from the Royal Bank.

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The Prime Minister also employed his sharpest and bluntest language so far to criticize the conduct of Mr. Duffy, a man who has turned on his party and accused it of a coverup.

"Mr. Duffy took $90,000 of expense money he did not actually incur. He was told to pay it back. He committed to paying it back. He said publicly he had paid it back," Mr. Harper told the Commons.

"That turned out … to be a story told by Mr. Duffy and Mr. Wright," the Prime Minister said.

"As a consequence, Mr. Wright no longer works on the public payroll. Mr. Duffy should not be on the public payroll either."

Mr. Harper has repeatedly denied knowing that his chief of staff gave the $90,000 to the PEI senator and he dismissed Mr. Wright from his post in mid-May after first defending his top aide.

Mr. Mulcair challenged Mr. Harper, noting that he was silent on Conservative Senator Carolyn Stewart Olsen. "Today the Prime Minister insisted, and said, that anyone who does that should not be on the public payroll. That is what he just repeated, something he had said yesterday.

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"Carolyn Stewart Olsen charged $64,000 in expenses for a home she has lived in for decades. Why is she still on the public payroll?" the NDP chief asked.

Mr. Duffy, Ms. Wallin and Mr. Brazeau, all Harper appointees to the Senate, are all under investigation by the RCMP. None have been charged or found guilty under the law.

The Prime Minister also pointed out that Mr. Duffy has not reimbursed Mr. Wright for the gift.

"The reality is that Duffy still has not paid a cent back to the taxpayers of Canada. He should be paying that money back," Mr. Harper said.

"The fact that he hasn't and the fact that he shows absolutely no regret for his actions means he should be removed from the public payroll."

With a report from Kim Mackrael