Senator Mike Duffy's lawyer is appealing to the "good parliamentarians" in the Red Chamber to quash a demand his client repay $16,955 in ineligible expenses.

The committee that oversees Senate spending and administration sent the Prince Edward Island senator a letter outlining the problematic expenses, despite Duffy being cleared of 31 charges of fraud, breach of trust and bribery related to his expenses last April.

"He shouldn't have to go through this. It's absurd. The judgment is final," Donald Bayne told Rosemary Barton, host of CBC News Networks' Power & Politics, on Thursday.

In the letter, Nicole Proulx, the clerk of the Senate's internal economy committee, writes that despite the fact Duffy, a non-affiliated member, was cleared of criminal charges, "new information surfaced in the public domain" warranting an assessment of the senator's expenses.

The flagged expenses, between the period of March 5, 2009, and Sept. 13, 2012, include personal photos, makeup and Duffy's personal trainer, all raised during Duffy's long court trial.

But the demand isn't unanimous. CBC News has learned a number of senators both on and off the Senate's committee on internal economy, budgets and administration didn't want to issue another bill to Duffy.

Donald Bayne says Senator Mike Duffy has already had his day in court. (CBC)

A Senate source told CBC the chief financial officer of the Senate heard about the additional expenses during the trial and decided it was her duty to comb back through his expenses.

The CFO alerted the internal board, which met on June 7 and found Duffy had broken Senate administrative rules. Bayne said Duffy wasn't given a chance to weigh in before he received the letter.

The defence lawyer said he sent out a copy of his response to senators and members of the media hoping most senators will back down.

"I don't believe for a minute that this action represents the considered judgment of all or most senators — many or most of whom are good parliamentarians" Bayne said.

"I'm hoping and trusting that senators will reflect on this and say, 'Wait a minute we want a voice on this. This is inappropriate.'"

Move 'unwise' warns Bayne

Duffy became one of the faces of the Senate expenses scandal in 2014 after he was charged with offences linked to his living claims. He was suspended, but was cleared in April by Justice Charles Vaillancourt.

In his 15-page response letter to Proulx, Bayne reminded the committee that Vaillancourt reviewed the claims they are now seeking and still cleared Duffy.

"This is double jeopardy," Bayne said. "It's frankly quite unwise."

Bayne points out Duffy remained under suspension until August 2015, suffering a net loss of over $155,000.

"A very significant monetary and other penalty has, therefore, already and improperly been imposed by the Senate standing committee upon Senator Duffy," said Bayne.

"This unjust suspension and severe economic and reputational penalty was imposed on a man known to be confronting grave health issues exacerbated by stress."

But Senator Vernon White argues there's a difference between expenses being criminal, and being plain wrong.

"If it doesn't fit within our rules as an expense, you shouldn't be paid for the expense," the Conservative senator said.

Carignan, Tkachuk, Housakos named

In his letter, Bayne hurled criticism at the very committee he's writing to, reminding it the judge "criticized Senate leaders for unjustly doing the bidding of the office of the then prime minister," Stephen Harper.

He stressed that 30 senators were flagged for questionable spending, including Claude Carignan, who moved to suspend Duffy, David Tkachuk, the former chair of the internal economy committee, and Leo Housakos, the current chair.

"Senator Carignan never moved his own suspension or that of any of the other 29 senators," wrote Bayne.

A joint statement from Housakos and Senator Jane Cordy, deputy chair of the committee, on Thursday said the letter submitted by Duffy through his lawyer will be taken into consideration.

"​The dispute resolution process is an independent, arm's-length process that ensures senators are not sitting in judgment of other senators. This process is being adhered to in Senator Duffy's case exactly as it has been for all senators since its implementation," reads the statement.

CBC News learned a handful of senators also thought the auditor general should be brought in to go through the expenses of all four senators swept up in the expense scandal — Duffy, Pamela Wallin, Patrick Brazeau and Mac Harb — because their audits had been conducted by an outside firm and not the auditor general. But that idea has since been abandoned.

The RCMP already announced they won't press criminal charges against Wallin, while charges against Harb were withdrawn. Brazeau has been charged and is still awaiting trial.

Bayne said if it's a "less wise Senate" than he thinks it is, Duffy will have to take his case to the independent arbitrator, former Supreme Court justice Ian Binnie.

When asked if Duffy himself is considering legal action to win back lost salary, Bayne kept his cards close.

"That is being closely looked at."