Senator Mike Duffy is eligible for his Prince Edward Island seat in the Senate, his party's Senate leader said Thursday.

A Senate committee looking at residency expenses had asked for legal advice on whether Duffy met the requirements to be a P.E.I. senator after it was revealed he lives mostly in Ottawa.

The Constitution says senators shall reside in the province from which they're appointed.

Marjory LeBreton, government leader in the Senate, says the legal advice they received is that signing a declaration of qualification form that says he is from the island is all it takes.

"There is no doubt that senators that sit in the Senate, by way of the declaration of qualification, qualify to sit in the Senate," LeBreton said.

But while the Senate has settled the question of whether Duffy qualifies for his seat, questions over his expenses â€” and those of other senators — remain.

Expenses audit continues

The expenses of Duffy, Pamela Wallin, Mac Harb and Patrick Brazeau have been sent off for a forensic audit following an internal review of senators spending, CBC News has learned.

The Senate's internal economy committee has reviewed the expenses of all 98 senators in office last December when they announced the review and cleared all but those four, the CBC's James Cudmore is reporting.

Nunavut Senator Dennis Patterson, who also owns property in British Columbia, was deemed to be a primary resident of the territory by the Senate internal economy committee, David Tkachuk, the committee's chair, told the Senate Thursday.

LeBreton admitted the expenses scandal hasn't helped the Senate's reputation.

"It's very disappointing to me," she said.

"Anything that I can do to strengthen the rules, clarify and strengthen, there's no one in this building more than me that wants to tighten all this up."

Senate Liberal Leader James Cowan said Thursday that four senators, whom he didn't name, were subject to an outside audit. He promised the results would be made public, but didn't know when the results of the audits could be expected.

Tkachuk told the Senate that the committee screened all 98 senators who were in office in December when they decided to audit primary residences. There were five vacant seats at the time and two senators about to retire.

The report tabled by Tkachuk's committee says three senators were referred for the outside audit because of their secondary residence expenses. A fourth senator's travel claims were referred for an outside audit, but are not considered part of the review by the internal economy committee.

Some travel claims reviewed

The travel claims of Patterson and Liberal Senator Rod Zimmer were also reviewed, but the committee was satisfied the claims were in order, the report says.

Senators are eligible this year for up to $22,000 to cover their living expenses in the capital if their primary residence is more than 100 kilometres outside the Ottawa-Gatineau region.

All senators were asked to submit copies of their health card, driver's licence and one page of their tax filings, as well as a signed statement of where they vote, Tkachuk said. The committee also reviewed travel patterns through each senator's primary residence.

The committee is recommending that the Senate require senators to show their driver's licence, health card and income tax every time they sign their declaration of primary residence, and that they have to sign the declaration every year.

It's also recommending that Senate management standardize terminology in Senate policy, and review the travel policy to comply with primary residence declarations.

with files from James Cudmore