New Zealand Prime Minister John Key ordered Thursday an inquiry into his cabinet ministers’ expenses after one of them resigned, admitting that he had used his ministerial credit card for personal purchases.

Mr. Key told a news conference that the auditor-general would review all expenditures by former housing and fisheries minister Phil Heatley and “look at the systems and processes for dealing with ministerial expenses to ensure we are doing everything possible to make sure the rules are clear and are being followed.” Announcing his resignation from the cabinet, Mr. Heatley, 42, told journalists: “I believe I’ve failed to live up to my own standard, and for that I’m embarrassed and immensely sorry.” He said he would remain in Parliament as a National Party backbencher.

Mr. Heatley said Tuesday that he had apologised to Mr. Key and repaid more than 1,200 New Zealand dollars (880 US dollars) after a newspaper reported that he had used his taxpayer-funded ministerial credit card for personal expenses.

He resigned after it was revealed that he had put two bottles of wine on his card in August, claiming the 70 New Zealand dollars involved was for “food and beverages” for himself and his wife.

In fact, no food was included in the purchase, and, worse, the occasion was not a ministerial function but the annual conference of the ruling National Party.

Mr. Key said it was an “unintentional error,” and Mr. Heatley’s actions were “untidy and careless,” but not dishonest.

He said that Mr. Heatley could regain his cabinet portfolios if Auditor-General Lyn Provost found no evidence of intention to defraud in her examination of his expenses since becoming a minister 18 months ago.

“Everyone is human, and from time to time people make mistakes,” Mr. Key said.

Provost would look at the entire system of ministerial expenses to ensure that everyone understood the rules and abided by them, Mr. Key said: “We are a cabinet that has high standards.” Gerry Brownlee, the third ranked minister in the cabinet and Minister for Economic Development, said Tuesday he had also apologised to the Prime Minister, repaid some personal expenditure he had charged to his ministerial card and returned it “so there can be no future confusion over what is and is not ministerial business.” Mr. Key said he had no reason to believe any other ministers had misused their cards, but the Auditor-General’s inquiry would establish that.

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