ACT leader John Banks did ask police not to publicly release his statement on the Kim Dotcom donations and opposed the publication of the entire file, documents reveal.

Banks' lawyer David Jones QC told police it would be used by his ''political adversaries'' and for ''irresponsible commentary.''

Banks has always insisted he had "nothing to fear, nothing to hide,'' over the donations scandal.

His statement was censored when police released their file on the investigation last month. Other statements, including that of Dotcom and his lawyer Greg Towers, were made public.

But confusion has remained over whether Banks requested his own testimony be kept secret.

In September his press secretary told a reporter that Banks was not responsible for what police released. But police contradicted this, saying police sought permission of witnesses before disclosure.

And documents obtained by Labour's deputy leader Grant Robertson show Jones requested his statement be withheld from a release under the Official Information Act.

On August 10, he wrote: ''As you know, the complaint against Mr Banks was politically motivated....the release of information from the investigation file would no doubt allow political adversaries of Mr Banks and media commentators alike to pore over such material and selectively highlight matters considered politically advantageous of 'newsworthy'.''

Jones went on: ''Given the level of uninformed and unbalanced criticism that occurred once the result of the investigation was made public, disclosure of the investigation file would no doubt bring about irresponsible commentary.''

He also argued it would ''bring the criminal justice system into disrepute.''

''Disclosure of any material relating to Mr Banks, or indeed any part of the investigation file is opposed.''

Prime Minister John Key has stood by his coalition partner.

Robertson said: ''This is further evidence that John Banks has lied to New Zealanders about this case.

''John Key said that if Mr Banks lied to him he would no longer have confidence in him as a minister. Mr Key needs to sack John Banks if he is to uphold standards of ministerial behaviour.''

Internet mogul Dotcom says he gave Banks $50,000 towards his 2010 bid to be Auckland mayor. But the donation - in two $25,000 cheques - was declared anonymous.

Police investigated but said although local electoral laws were broken they didn't have enough evidence to prosecute.

Banks was interviewed by detectives for three hours under formal caution in June.

The release of the file revealed a number of damaging details, including that Banks told Dotcom's lawyer in February that he couldn't support Dotcom because of his previous ''support'' during the election campaign.

Banks told the media he hardly knew the tech mogul - but Dotcom detailed how they'd had lunch together and Banks had even made a toast at his birthday party.

The police files also showed Banks was handed a $15,000 cheque by Sky City executives in a branded envelope. That donation was also registered anonymous.

The government has since tightened up the rules on local election donations.

- © Fairfax NZ News