Since the donations scandal broke in April, the Act MP has stuck to the mantra, "Nothing to fear, nothing to hide."
But he took a different approach when the Herald sought through the Official Information Act details from the police inquiry into his campaign for the Auckland mayoralty in 2010.
Statements from donors including internet tycoon Kim Dotcom and SkyCity casino boss Nigel Morrison were among those released.
Detective Inspector Mark Benefield, who led the investigation, said: "I ... enclose the statements of those witnesses who authorised disclosure." Mr Banks' statement was not included.
Police chief media adviser Grant Ogilvie said police sought permission from those interviewed before releasing statements. "The disclosures that were made were based on consent of those asked. That includes Mr Banks."
Mr Banks said it was the police who decided to keep his statement under wraps. Press secretary Shelley Mackey said: "Mr Banks is not responsible for what the police have released."
The documents released by police show Mr Banks was interviewed under formal caution in June. The police documents show two detectives interviewed Mr Banks, who was accompanied throughout by David Jones, QC.
Mr Banks is likely to face further questions after his press secretary removed his line of defence against the accusations.
Police said they could not prove that he knew the content of the form was false because it was filled out by the campaign treasurer, who assured Mr Banks it was "true and correct". Mr Banks then signed it.
Ms Mackey yesterday challenged descriptions of this as saying Mr Banks signed the form without reading it. In an email, she said: "But John Banks did read the document."
Police had already established Mr Banks knew who some anonymous donors were. Ms Mackey's statement meant he would have known the donation form did not include donors of whom he was personally aware.
She then back-pedalled, saying the treasurer had "gone over" the form with Mr Banks.
Prime Minister John Key said yesterday he would stand by Mr Banks and blamed the Labour Party for a "politically motivated attack". He said Mr Banks had not broken the law.
Labour deputy leader Grant Robertson said the Prime Minister was wrong and police found Mr Banks did break the law but could not be prosecuted because of a six-month time limit.
On the statements, he said Mr Banks should show the public what he had told police. "Everybody else has fronted up. Why hasn't he?"
Greens co-leader Russel Norman said Mr Banks should resign. "The Prime Minister should show some backbone and sack John Banks."
- David Fisher of the New Zealand Herald
