The general manager of the Parliamentary Service says the rules on MPs' allowances need to be cleared up.
Geoff Thorn has told Parliament's government administration select committee that the principles governing MPs' entitlements are being reviewed.
Mr Thorn said until the controversy over Finance Minister Bill English there had never been any concerns about the issue of an MP's primary place of residence.
He agreed, however, that there is some uncertainty about the definition of a primary place of residence.
He said the review should clarify what MPs are and are not entitled to.
Labour MP Chris Hipkins appeared to suggest in his questioning that some MPs might be milking the system by living in serviced apartments, but renting them out on the nights they weren't in Wellington.
Mr Thorn said if that is the case any money MPs made should be deducted from their accommodation allowance.