Prime Minister John Key has hinted that Labour's ministerial credit card records will reveal far higher levels of spending than those of his ministers.

Yesterday it was announced Phil Heatley would be reinstated to Cabinet after the Auditor-General's inquiry found that while he spent $1402 of taxpayers' money wrongly he did not intentionally break the rules.

Mr Heatley resigned his housing and fisheries and aquaculture portfolios on February 25 after admitting he misused his credit card.

Auditor-General Lyn Provost yesterday published her report on the audit into Mr Heatley's ministerial spending from when he became a minister in November 2008 until he quit.

While it found Mr Heatley did not intentionally break the rules, it said he could have been more careful and public trust was at stake.

Mr Heatley's temporary fall from grace occurred when Ministerial Services released government ministers' credit card statements with details on all spending.

Previously information released did not include any detail, but since the release, media organisations have requested the last government's credit card statements.

Mr Key said he had been told of what is to come.

"I understand from Ministerial Services they are working through boxes and boxes and boxes of information to release to you all (the press gallery) on previous Governments and their spending," Mr Key said

"I think what you are going to find it when you see it, is that the world has changed a lot from even the last regime. We are actually quite conservative and I suspect we will be a lot more conservative in the future."

Meanwhile, Mr Key brushed off further criticism of Mr Heatley over him requiring two ministerial cars to accompany him while he and his family took a train ride down the South Island.

Mr Key said he did not want to discuss an issue that had been dealt with by the Auditor-General.

"I was aware of it, it fits within the rules. But you know Mr Heatley, who has been restored to Cabinet, is under no illusions, like the rest of my ministers, that we expect high standards from them, to spend taxpayers money wisely and I expect them to be cautious."

Speaker Lockwood Smith today also defended a $14,800 allowance that all MPs get, and can spend on almost anything, saying any other system would be too complicated.

The Auditor-General's report highlighted that a $70 claim for wine Mr Heatley bought for his table at a National Party conference and wrongfully chalked up on his ministerial credit card could have legitimately come out of the MP allowance.

Dr Smith the $14,800 was built into salaries and no receipts or claims needed to be processed as any other system was administratively cumbersome.