A police investigation into donations to John Banks' mayoral campaign is complete - but any action is weeks away.

Detective Inspector Mark Benefield said a report had been sent to Police Legal Services for review.

All high profile cases are assessed in this way, he said. But he gave no hint as to what conclusion police have drawn.

It was likely to be at least two or three weeks before the assessment was complete, he said.

Officers also wrote to complainant Labour MP Trevor Mallard, informing him of the move.

Banks came under scrutiny after it was alleged he knew a $50,000 anonymous donation to his 2010 campaign fund came from Kim Dotcom.

Police were also looking at a $15,000 anonymous donation believed to have come from SkyCity casinos.

Banks has insisted he did not break local electoral laws and said he has nothing to hide.

- © Fairfax NZ News