The Department of Labour set up a three-strong inquiry team to find out why staff released information to the Herald about its investigation of National MP Kanwaljit Singh Bakshi without getting Immigration Minister Jonathan Coleman's permission first.

The Official Information Act release showed an immigration investigator suspected that Mr Bakshi or one of his supporters "paid off" the Indian couple at the centre of allegations that he made bogus job offers as part of an alleged scam.

Dr Coleman yesterday said the internal inquiry was called because "that OIA didn't come through my office as every other OIA should".

The minister said the department had assured him this was "incompetence" rather than an attempt to bypass his office. He said there had been no "political interference" to stop information about his National Party colleague Mr Bakshi being released.

Labour immigration spokesman Pete Hodgson said Dr Coleman should be "entirely unbiased", and leave the OIA requests to the department.

"He's done precisely the opposite and in doing so has signalled loud and clear he wants a hands-on approach to managing issues around his own colleague," said Mr Hodgson.

The internal inquiry was revealed in further documents about the investigation of Mr Bakshi the Herald obtained yesterday from the Department of Labour, which oversees Immigration NZ.

The documents show a three-person inquiry team based in Auckland and Wellington was set up to investigate the original release. They name nine staff involved and say there may have been a number of breaches of the department's policies and practices. A major issue was the lack of a "risk escalation" notification being put on the request for information about the investigation of Mr Bakshi.

The Department of Labour refused to say if the inquiry was finished or if any staff had faced disciplinary action.

The documents also show that the Department of Labour called off a planned interview with the Herald about the investigation after Dr Coleman's ministerial adviser James Watson intervened.

Mr Bakshi was investigated after the Indian couple alleged he made the wife a false job offer to help her migrate to New Zealand. The couple later refused to co-operate when interviewed in India with the investigator forming "an impression that [they] may have been paid off by Bakshi or one of his supporters".

Mr Bakshi has denied paying off the couple but said he could not rule out a "wellwisher" acting without his knowledge. The investigation was closed because of "insufficient evidence".

Dr Coleman said if new evidence was presented he would expect the Department of Labour to investigate.