Liberal Senate Leader James Cowan argued late Tuesday night that the committee on internal economy had lost credibility with Canadians and the police should take over.
He said the initial report the on former Conservative senator's expenses had been "whitewashed" by his Tory colleagues, and then further thrown into doubt when it was discovered the $90,000 owed by Duffy was paid by the prime minister's former chief of staff Nigel Wright.
"What confidence can we have that they will allowed to do their work without political interference from outside, from the leadership in the Senate, or the House of Commons or the prime minister's office," Cowan said on the Senate floor.
"From what we have witnessed to date, we don't believe Canadians would have any confidence in this proposed approach."
But Senate Speaker Noel Kinsella ruled Cowan's bid was out of order, and emphasized that the committee could always refer the matter to the police later.
The Conservative majority in the Senate voted to have the matter sent back to the committee.
The Liberals are also trying another tack — trying to trigger special parliamentary hearings in the hopes of forcing Wright and others to testify about the $90,000 payment to Duffy.
Cowan argued that Stephen Harper's office violated the sacrosanct privileges of parliamentarians, and may well be in contempt of Parliament.
Wright resigned Sunday, and Duffy quit the Conservative caucus last Thursday, after the details of their transaction began to emerge.
After that payment from Wright, Duffy stopped co-operating with an audit into his expenses. The Senate report into Duffy does not include some of the same language used in nearly identical reports into the claims of senators Patrick Brazeau and Mac Harb.
Liberals on the Senate committee handling the report voted against it in protest.
"If monies were paid which would influence the decision of a Senate committee, then that is contempt of Parliament, and that infringes my privileges as a senator, and it infringes the privileges of senators and the Senate and interferes in a spectacular way...with the independence of the Senate," Cowan told reporters.
Conservative Senate leader Marjory LeBreton had declared the matter closed two weeks ago when the reports on housing expenses were tabled.
During Senate question period on Tuesday, LeBreton insisted that she and her colleagues were unaware of Wright's payment to Duffy until it was revealed on the news.
"I was dealing with what I had at that point in time. That's all I could do," LeBreton said of her comments on May 9.
Cowan pressed LeBreton to explain why the report on Duffy's claims was different from that of Harb and Brazeau.
LeBreton suggested it was because Duffy had already paid his improper expenses, and the reports might have been designed to persuade Brazeau and Harb to do the same.
Cowan is arguing that the executive branch interfered in the proceedings of the Senate committee tasked with studying Duffy's expense claims.
Claude Carignan, the Conservative deputy leader in the Senate, rejected the notion the Senate's privileges had been violated. He said it was enough that the Senate ethics officer and the conflict of interest and ethics commissioner were reviewing the matter.
"I think this is a serious issue, and it shouldn't be an issue of partisanship," said Carignan. "There is a parliamentary process created to treat issues of this type, and I think we should allow it to unfold."
If Kinsella finds there appears to be a breach of parliamentary privilege, he could send the issue to a special committee for further study.
Such a Senate committee would enjoy the privilege of summoning any witness it wants on the matter, including Wright or others from Harper's office.
Kinsella said late Tuesday evening he was taking the matter under advisement.
Harper's office insisted Tuesday there was no agreement between Wright and Duffy, and that as a result no documentation of such a deal exists. But no one has yet provided a full explanation of what transpired between the two men.
Meanwhile, Harb raised a question of privilege in the Senate on Tuesday evening, suggesting his reputation was impugned when the Senate committee issued its report saying he owed $51,482. Harb noted that independent auditors declared rules around primary residences were not clear, and they did not determine he had broken them.
"Tell me what percentage of the time you want me to live in my primary residence?" Harb responded angrily to questions put by Liberal Senator George Furey.
"This is a democracy. If I'm not billing the Senate for my time off it's not anyone's business where I am."
The report into Brazeau's expenses was passed by the Senate late Tuesday. Brazeau has been asked to pay $48,744. He is also fighting the bill.
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