Speaker Lockwood Smith said he will not hesitate to refer Pansy Wong to the police if a Parliamentary Service investigation into her travel perks comes up with serious misuse.
Dr Smith said he did not wish to discuss Ms Wong's case specifically but promised the investigation would be thorough.
"You'll be aware there was a case of a former member I put in the hands of the police and I will do that if I find serious issues."
The former MP is understood to be Roger McClay, who was sentenced to community service for claiming the rebate while also claiming mileage for travel for charities.
Yesterday the Speaker would not confirm if Parliamentary Service had extended its investigation of Ms Wong's overseas travel rebates to also include domestic travel by her husband Sammy Wong.
MPs' partners also have unlimited domestic travel but, as with the international rebates, cannot use it for private business.
Ms Wong resigned as a minister last week after it was revealed her husband had conducted business while on a late-2008 holiday to China with Ms Wong, which was paid for using 90 per cent discounts. Ms Wong has not yet spoken publicly about allegations against her, which include further claims by Labour that she had promoted her husband's business while meeting officials as a minister on the same trip.
Yesterday Labour leader Phil Goff said the investigation should be widened to look at all entitlements used by Ms Wong and her husband.
"Given the evidence that has already emerged, it's clear the Wongs have been unable to distinguish between their taxpayer-funded entitlements and their pursuit of private business interests despite the rules being crystal-clear.
"So a more detailed investigation is certainly warranted."
Mr Goff said police could also take action of their own accord rather than wait for a matter to be referred to them.
Dr Smith yesterday scrapped the overseas holiday perks for MPs after a request from the Prime Minister with broad political consensus.
The Remuneration Authority is due to decide whether MPs should get a pay increase next month and will also have to decide whether to compensate for the loss of the perk in its decision.
Yesterday Mr Key said he had told the Remuneration Authority he did not believe MPs should get a pay rise this year. It would be the second year running of zero pay increases for MPs after they also asked the authority last year for a nil increase because of the recession. Although the authority is independent, it has to consult MPs before making its decision.
Mr Key said if the authority felt it had to give any increase it should be minimal.
"I don't think MPs can justify getting lavish pay increases when the rest of the country is living with 1 and 2 per cent pay increases," he said.
He had asked for the overseas holiday perk to go on Monday and said yesterday he was pleased it had happened.
While MPs who had used it would lose something, it would make little difference to those who had not.
"We can't stop it going to the Remuneration Authority, but I hope they don't have a rush of blood to the head and decide MPs need a lot of money because it's been abolished."
Although the perks will no longer be available for private travel, a new scheme to fund parliamentary business-related travel will be set up.