Government staff are not yet halfway through the "mammoth task" of compiling the previous Government's credit card records for release to the media and public, an exercise which is expected to cost about $50,000 and take a further two months.

The Department of Internal Affairs is compiling about 7000 documents detailing spending by Helen Clark's ministers on their taxpayer-funded credit cards after receiving more than a dozen requests from media for the information under the Official Information Act.

The requests followed the earlier release of the current Government's credit card records which revealed Whangarei MP Phil Heatley's unauthorised $70 wine purchase and cost him his ministerial portfolios late last month.

Internal Affairs spokesman Allen Walley said the Labour Government information would be released in May.

The "mammoth task", now "only about 20 per cent" complete, is perhaps the bulkiest release of material under the OIA and its completion will be delayed by the legal requirement to remove information such as phone and credit card numbers from documents.

Former ministers, including those who are no longer MPs, will get to see the information before it is released to the media, but they have no ability to have content removed. "There's no get-out clause."

Mr Walley said the information had not yet been seen by former ministers.

A spokesman for Labour leader Phil Goff said he "has made it clear that if there are any cases of inappropriate spending he expects it to be repaid".

Mr Walley said where items had been repaid by former ministers subsequent to receiving the OIA information, that would be "absolutely" obvious.

The decision to release the information was made by the department in light of the high level of interest shown in the current Government's credit card records, "and therefore it was decided to go to the lengths that the department is going to to release this information". It was "not at all" at the request of any current minister.

According to a convention detailed in the Cabinet Manual, copies of the previous Government's documents to be released under the OIA go to the current Administration.

The Leader of the Opposition will have the opportunity to "express any concerns about the release of the documents which may be considered by the department releasing the information".

The time limit for responding to the request for information may be extended to allow completion of this consultation.

Deputy Ombudsman Leo Donnelly said the decision to release ministers' credit card records under the OIA might have implications for other elected and non-elected officials, including those in local government.

"Clearly the decision does not so much establish a precedent but reflects an acceptance of the principle that such information can and should be disclosed to the public."