The Prime Minister says he will wait for the outcome of the Auditor-General's report into Phil Heatley's credit card spending before commenting further on the National MP's future.
A day after he resigned from the Cabinet, the Dominion Post has reported that the MP for Whangarei was repeatedly warned by officials about the use of his ministerial credit card.
Mr Heatley quit his portfolios in housing and fisheries on Thursday after admitting to signing off on an inaccurate expense claim. He had mis-used his ministerial card and signed a receipt for a purchase of food and beverage, when only wine was involved.
The MP claimed he had just made mistakes, which was accepted by Prime Minister John Key.
When asked for his response about the warnings, Mr Key said an independent inquiry is now under way and he does not want to prejudge the process.
The Prime Minister says he did not ask Mr Heatley to resign and is keeping the door open to a possible return to the Cabinet, depending on the outcome of the Auditor-General's investigation.
Mr Key has asked the Auditor-General and Ministerial Services to look at the way the expenses of ministers are handled.
Mr Heatley, who has also asked the Auditor-General to look into his accounts, did not return Radio New Zealand's calls on Friday.
Green Party co-leader Metiria Turei says the whole episode reinforces the need for an independent review of allowances and expenses for MPs and ministers.
Heatley 'repeatedly' warned over use of card
Documents published by The Dominion Post reveal that Mr Heatley was repeatedly warned by officials about the use of his ministerial credit card.
The resignation as Cabinet minister followed several other instances of Mr Heatley clearly breaching the rules around ministerial credit cards.
These included taking his family on a trip around the South Island and shouting wine at a National Party conference.
Mr Heatley claimed they were all mistakes, and he was not as familiar with the rules as he should have been.
But documents from Internal Affairs show Mr Heatley was warned in writing several times about how he was using his ministerial card.
The letters directed him to read the rules, which state the card is for official business only and reimbursement for personal spending is not allowed.