Police have completed their investigation into mayoral donations ACT MP John Banks received in 2010, but are taking legal advice before announcing their findings.

Mr Banks was investigated following claims he knew donations to his failed Auckland mayoral campaign came from piracy accused millionaire Kim Dotcom and SkyCity, but declared them anonymous.

Dotcom gave $50,000, which Mr Banks reportedly asked to be split into two $25,000 cheques, while SkyCity gave $15,000 to Mr Banks and to the inevitable election winner, Auckland Mayor Len Brown - who declared the source of his donation.

Mr Banks had previously offered help to Dotcom as he sought to buy the $30 million mansion in Coatesville, north of Auckland.

Mr Banks also asked Dotcom for a donation to the ACT Party before last year's election, promising to be "a very good friend" once he was in parliament, but was told to "go get f*****".

Detective Inspector Mark Benefield told Fairfax that police have finished their investigation into the donations and a report has been sent to Police Legal Services for review.

He said all high-profile cases were assessed that way.

It was likely to take two to three weeks for the assessment to be completed.

Mr Banks denied any wrongdoing, and Prime Minister John Key refused to stand Mr Banks down as a minister, saying he takes him at his word.