Prime Minister Stephen Harper mounted a vigorous defence in question period on Wednesday against explosive remarks made yesterday by Senator Mike Duffy in the ongoing Senate expenses scandal.

Duffy alleged, in a speech to the Senate on Tuesday, there was a Conservative scheme to have him removed from the upper chamber unless he went along with a plan to repay his Senate expenses, although he believed he had followed the rules.

Less than 24 hours after Duffy made those remarks, the prime minister denied Duffy's allegation that he was more concerned about the perception of Duffy's expenses in the media than whether he violated parliamentary rules because the expense rules were “inexplicable to our base."

Harper rebutted Duffy's version of events saying, "the issue is not a matter of perception … you can not claim an expense you did not incur. That is not right, that is not proper, and that will not be tolerated in this party."

Duffy said on Tuesday, that "elaborate undertakings" were negotiated among several key players including officials in the Prime Minister's Office, the Senate leadership, his own lawyer, a Conservative Party lawyer and lawyers from the PMO.

On Wednesday, Harper rose to answer every question put to him not only by the opposition leaders but by every MP, suggesting Duffy's remarks may have had an impact on the Conservative base.

For Harper, it was a deliberate change of tactic from the day before when he let Paul Calandra, his parliamentary secretary, answer many of the questions in his place.

Duffy also said on Tuesday that he had a meeting with the prime minister and Wright after caucus on Feb. 13 where Harper ordered Duffy to repay his ineligible expenses.

The prime minister did not deny having asked Duffy to repay his expenses but rather seized the opportunity to accuse Duffy of playing the victim card.

"Mr. Duffy now says he is a victim because I told him he should repay his expenses. You're darn right I told him to repay his expenses," Harper said.

You're darn right I told him to repay his expenses. - Prime Minister Stephen Harper

Harper said he made his statements "not just to Mr. Duffy and Mr. Wright but many others who were present and who heard them."

According to Duffy, it was Harper — not Wright — who provided the political solution that Duffy's expenses must be repaid.

The prime minister has consistently maintained that Wright acted alone when he decided to cut Duffy a cheque.

On Tuesday, Duffy also listed names of people involved in negotiating the alleged scheme to have him repay the expenses.

Mulcair asked Harper, during question period, to name the Conservatives allegedly involved in the scheme but the prime minister would only say that Wright had already addressed that question directly.

The number of people that Wright said he informed, according to court documents, is far lower than the number of people Duffy cited, Harper said.

Harper said he did not threaten Duffy with expulsion but he did expect the senator to repay his expenses "and not Mr. Wright to repay them for him."

The prime minister also reiterated his position that he knew nothing about the $90,000 cheque Nigel Wright, the prime minister's former chief of staff, gave to the senator to repay his ineligible expenses.

"Any assertion that I was in any way consulted, or had any knowledge of Mr. Wright's payment to Mr. Duffy, is categorically false," Harper said.

Harper said, as he had in the past, that had he known about Wright's decision to give Duffy the money he would not have permitted it, and that as soon as he was made aware of the $90,000 cheque on May 15, he revealed it to the public.

Earlier in the day, Conservative MPs emerged from their weekly caucus meeting saying they believed the prime minister's version of events over Duffy's.

Duffy Senate scandal 'directly implicates' PM

But NDP Leader Tom Mulcair told reporters after a meeting with his caucus that Duffy's speech in the Senate on Tuesday puts the prime minister directly at the centre of the Senate expenses scandal.

"This is a profound scandal that directly implicates Stephen Harper," Mulcair said during a scrum on Parliament Hill.

Mulcair said the Senate expenses scandal is no longer about the $90,000 cheque Nigel Wright, Harper's former chief of staff, gave to Duffy to repay his ineligible expenses.

"This is about Stephen Harper. He has to start telling the truth to the public. The public has a right to know," Mulcair said.

During question period, Mulcair asked Harper whether he had any involvement in the Senate's motion to have Senators Duffy, Patrick Brazeau and Pamela Wallin suspended without pay from the upper chamber.

Harper said the Senate leadership had the motion approved by the Conservative Senate caucus, a motion he said he fully supported.

"I fully support the motion. I do not believe that under the circumstances these individuals should be on the public payroll," Harper said.

After a meeting with his caucus, Liberal Leader Justin Trudeau said it was time the prime minister showed some leadership.

"A leader takes responsibility when things go wrong and this prime minister has consistently avoided taking any responsibility for this sordid mess," Trudeau told reporters gathered on Parliament Hill.

While Harper fired back at Duffy in the Commons on Wednesday, Wallin was in the Senate defending herself against the motion that would have her suspended without pay.