The RCMP is set to examine the spending of three senators after external audits of their expenses revealed they billed thousands of dollars in ineligible housing expenses, says the Leader of the Opposition in the Senate.

In an interview on CBC Radio's The House, Liberal Senator James Cowan said the Mounties are looking at the Deloitte audits into the primary and secondary residences of Senators Patrick Brazeau, Mike Duffy and Mac Harb.

"I understand that they're looking at it. I understand that they've been following this case very closely and they will be reviewing the documents that weren't available until Thursday afternoon," said Cowan on Saturday.

Based on the Deloitte audits, a Senate committee report released Thursday recommended Brazeau must repay $48,744 and Harb $51,482 for housing and mileage expenses.

The report also noted Duffy had already repaid $90,000 in claims in March when it became apparent to him that he "may have made a mistake" in filling out his expense forms.

"It's my understanding that they [the RCMP] have been following this closely and they will review the documents that were filed in the Senate on Thursday. As is entirely appropriate," Cowan said.

Senators who live more than 100 kilometres from Ottawa are allowed to claim housing expenses of up to $22,000 a year.

According to Cowan, the Senate could take further disciplinary action against the senators and a criminal investigation may also be warranted.

"I'm just out to make sure that there is due process followed. And if there are offences under the Criminal Code that those are pursued," Cowan said.

Changing the rules

Cowan and the Leader of the Government in the Senate initiated the probe together, though Conservative Senator Marjory LeBreton doesn't see the need for the police to investigate.

The Senate's "archaic rules" are to blame for the confusion, said LeBreton.

"The fact is, and the auditors have pointed this out, some of the rules were unclear — and are unclear."

According to LeBreton, having the senators pay back the claims with interest is good enough.

"We have now brought in very, very strict new rules so there can be no doubt," LeBreton said.

The Senate report recommended that rules about claiming per diems should be changed and that senators should have to provide receipts for all taxi use. Previously, senators could claim up to $30 without a receipt.

The proposed new rules, according to LeBreton, "will clear this up, once and for all."

Harb disputed the Senate report's findings and retained a lawyer immediately after it was released.

Brazeau, a former Conservative who now sits as an Independent, is currently suspended from the Senate over a criminal charge in a separate matter.

Cowan said he is reserving judgment until he hears from all the senators involved but would like to see Duffy appear before the Senate to explain what was so confusing when he filled out his expense forms.

"I would like to hear him explain what it is in the forms that he found confusing," Cowan said.

Parliament resumes on May 21 after the Victoria Day long weekend.