Former senator Lowell Murray, who was government leader in the upper chamber during the Mulroney years, tells CTV Question Period he believes the senate expenses scandal has been “very damaging” to the institution and there needs to be an open debate on the matter.

“Whether it’s fatal or not I don’t know,” Murray told CTVQP host Kevin Newman. “That’s another kind of constitutional question that will be fatal in terms of public opinion and really for their own reputation and self-respect all these good people have got to search their own minds and hearts and take a part in a debate that really shouldn’t be whipped.

“It’s got to be one where Senators are free to express their views on what has happened and what they expect to be done, whether there are further sanctions that have got to be taken against various Senators.”

The Harper government has so far defended Conservative Sen. Mike Duffy for showing "leadership" by repaying $90,000 in living expenses.

Duffy has said confusing paperwork caused him to mistakenly claim his primary residence was in Prince Edward Island, not Ottawa, where he has lived for years, and Senate government leader Marjory LeBreton backed up that assessment and promised clearer rules.

Liberal Mac Harb and Independent Patrick Brazeau were ordered Thursday by the Senate’s internal audit committee to pay back housing and mileage expenses, plus interest, that they claimed dating back to April 1, 2011. That ruling came after independent audits of the three senators’ expenses.

Senators can claim an annual housing allowance of up to $22,000 if their primary residence is more than 100 kilometres outside of Ottawa.

CTV News reported Friday that the RCMP is set to conduct a criminal investigation into improper spending by three senators whose expense filings were the subject of external audit

“…This business reflects badly on an awful lot of very good Senators who are extremely capable and are doing far better work, making a far better contribution to legislation and policy than they’re given credit for,” Murray said.

Murray believes Prime Minister Stephen Harper and LeBreton will have to deal more firmly with the situation.

“Harper, whatever any one may say about his policies or his governance, there’s never been a breath of scandal attached to him personally and why should he wear this?” Murray said. “The short answer is he shouldn’t and he’ll find out in a matter of days this is going down very badly, and he’s going to have to find a way, which I’m sure he will, to disassociate himself, to cut people off. “

That might involve some reflection on Duffy’s future. He serves in the Senate as a representative of Prince Edward Island, and the auditor’s report casts doubt on his constitutional residency requirement.

“It turns out from the auditor’s report that Senator Duffy does not pay his income taxes from Prince Edward Island, I presume he does that from Ontario,” Murray said. “And when you file your income tax as you know, you have to sign a declaration saying, I am a resident in whatever province. If he signed a solemn declaration saying he was a resident of Ontario then it’s hard to see how he is remains eligible to represent P.E.I. in the Senate"