David Tkachuk and Carolyn Stewart Olsen, who both sit on a committee reviewing improper expense claims by senators, were responding to a CTV News report.
The report alleges that Tkachuk and Stewart Olsen pressed Duffy to accept a secret $90,000 cheque from Nigel Wright, then the prime minister's chief of staff. Duffy was allegedly then expected to pass the money off as his own.
"The CTV News report is false," Tkachuk and Stewart Olsen said in an emailed statement. "At no time did we have knowledge of Mr. Wright's payment to Sen. Duffy before it was reported publicly.
"Anyone who suggests that we were aware of Mr. Wright's payment to Sen. Duffy before it was reported publicly is lying. Our long-standing position is that Sen. Duffy should have immediately repaid all ineligible expenses to taxpayers."
The CTV News report paraphrased emails shown to the agency by an anonymous source. They said Tkachuk allegedly told Duffy that if he went along with Wright's offer, the Senate would go easy on the audit of his living expenses and drop the question of whether he was actually a resident of P.E.I.
The details of the $90,000 were first revealed by the same CTV News reporter, Robert Fife, in May. Wright's lawyers, quoted in RCMP court documents, said he only discussed the payment with three other people inside Harper's office.
On Tuesday, a former deputy chief of staff to Harper weighed in on Twitter about who he believed.
"I've said it before, but I will take Dave Tkachuk's word over Mike Duffy's on any topic and at any time," wrote Derek Vanstone, now a vice-president at Air Canada, adding the hashtag "WhyDoesn'tDuffJustResign."
Former Liberal senator Mac Harb resigned from the Senate on Monday, after repaying a total of $231,000 in living expenses.
Larry Campbell, a Liberal senator and former Mountie who sits on the Senate committee with Tkachuk and Stewart Olsen, says it should look into the new allegations.
Liberal Senate Leader James Cowan said the RCMP, which is already investigating the circumstances around the Duffy payment, "would get to the bottom of this."
"That's why we were anxious right from the very beginning to send this to the RCMP and perhaps why the government was so resistant (initially)," he said in an interview.
It's not the first time that Tkachuk and Stewart Olsen have been accused of helping to cover up or whitewash the improper expenses claimed by Duffy and former Conservative Pamela Wallin.
A report into Duffy's expenses was stripped of its most pointed language by the Tory majority on the internal economy committee, while nearly identical reports into senators Patrick Brazeau and Harb included that language. The senators explained it was because Brazeau and Harb had not yet repaid funds owing.
Tkachuk also advised Duffy that independent auditors had discovered he had been in Florida while claiming to be on Senate business. He also wrote to Duffy on behalf of the committee counselling against meeting the auditors, saying that would only delay the process.
Tkachuk advised Wallin that when she dealt with auditors, she should omit any information from her calendar that was not relevant to the claims under scrutiny. That discussion also occurred before auditors had finished their work.
Also on HuffPost