The prime minister made the blanket assertion Wednesday amid a furor over the alleged misuse of a housing allowance meant to compensate senators who keep a secondary residence in the nation's capital.
The expenses scandal has mushroomed into a broader issue of whether several Conservative senators — Mike Duffy, Pamela Wallin and Dennis Patterson, all appointed by Harper — are entitled to sit in the Senate at all.
Questions have been raised as to whether they spend sufficient time in their home provinces or territory to meet the constitutional residency requirement.
"All senators conform to the residency requirements," Harper told the House of Commons.
"That is the basis on which they are appointed to the Senate and those requirements have been clear for 150 years."
In fact, the residency requirement has never been defined and its meaning has become increasingly muddied by the expenses scandal.
The Constitution stipulates that a senator must reside in and own at least $4,000 worth of property in the province or territory he or she was appointed to represent. It does not define what is meant by reside.
A government official said Harper interprets the residency requirement to mean that senators must "own residences and maintain deep ties" to their home province.
Opposition parties and even some Conservative senators insist the standard is higher, that senators' primary residences should be in their home provinces.
For the purposes of verifying claims for the housing allowance, the Senate's internal economy committee has established that primary residence is the province or territory where a senator votes, pays income taxes, holds a driver's licence and is covered by health insurance.
If that standard was applied to the constitutional residency requirement, Duffy, Wallin and Patterson would all likely be ineligible to sit in the Senate.
Duffy, a longtime Ottawa homeowner, was appointed to represent Prince Edward Island, where he owns a cottage.
Wallin, who owns condos in Toronto and New York, was appointed to represent Saskatchewan, where she owns several properties.
Patterson, who owns a home in Vancouver and a condo in Ottawa, was appointed to represent Nunavut.
The internal economy committee is seeking a legal interpretation of the residency requirement.
Interim Liberal Leader Bob Rae said until that is done, it's premature for Harper to assert that all senators meet the requirement.
"I don't know where these people live. I don't know where they have their homes or the nature of their property or any of those questions," Rae said.
"So I think we should wait until we get some answers from the Senate as well as from the outside auditors as to where people actually live."
If there's no problem with the residency requirement, NDP Leader Tom Mulcair questioned why so many Conservative senators are refusing to publicly disclose documentation about their primary residences.
"Will the prime minister demand that his senators, members of his caucus, come clean with Canadians or is he going to keep covering up for them?" Mulcair said in the Commons.
Patterson, who fled from television cameras Tuesday, did stop to talk Wednesday. However, he refused to say which province or territory covers his public health insurance or where he pays his taxes.
"There's a process in place, I'm fully co-operating, the results will be made public," he said, adding that he's "in full compliance" with all rules and procedures.
"I don't think it's appropriate to be tried on national television."
Duffy and Patterson's claims for a $22,000 yearly housing allowance are under examination by a Senate committee. Duffy last week volunteered to repay his allowance, blaming confusing paperwork about his primary and secondary residences for his mistake in claiming the funds.
The housing allowance claims of Duffy, fellow Conservative Patrick Brazeau and Liberal Mac Harb are also being examined by an outside auditor.
Wallin has been audited for $321,000 in "other travel" expense claims since September 2010. She has reportedly repaid a substantial chunk of that money.
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