Questions have been raised over another donation to the 2010 Auckland mayoral campaign of Act leader John Banks which was listed as anonymous yet made out for a specific amount and purpose.
The donation records from Mr Banks 2010 campaign for the Auckland mayoralty list $15,690 being donated for radio advertising. It has prompted questions over how a donor would find out how to donate the right amount of money to cover a specific bill and still remain anonymous.
Labour MPs Trevor Mallard said Mr Banks should explain how an unknown donor managed to find out exactly how much money was needed to cover radio advertising costs. He said an alternative was that the donation was "in kind" - meaning the cost of the advertising was donated by the company which did the work.
Mr Mallard said the advertisements also had to be properly authorised before running. He said this would also raise awareness inside the campaign camp.
"It seems to me it can't be listed as anonymous."
The Weekend Herald has seen the expenses sheet filled in by Mr Banks which showed The Radio Bureau had done work worth $15,690. The expense is described as being for the "last three days election advertising schedule".
The Radio Bureau, a specialist advertising agency for radio stations run by The Radio Network and MediaWorks NZ, has not responded to calls.
Prime Minister John Key said yesterday he had not sought any further assurances from Mr Banks.
"He has given me a cast iron assurance he has complied with the local electoral law. As I have said all week, I'm not going to sack a minister for complying with the law."
Detectives are expected to visit Dotcom at some stage this week in Coatesville, north of Auckland, where he is on bail for an extradition hearing brought by the United States in connection with his now defunct internet file-sharing business MegaUpload.
They will seek to question him, his wife Mona and any staff over their connection to the donation scandal.
Dotcom has said Mr Banks asked for money for his 2010 election campaign, and was offered $50,000. He said the payment was divided at Mr Banks' request to disguise its origins. The $25,000 payments are listed with three others on Mr Banks' donation return.
The donation is one of three being investigated by police - the others are the "radio advertising" donation and a $15,000 contribution from SkyCity casino.
Mr Banks, who also lobbied for Dotcom and provided feedback, has denied any wrong-doing.
•When Mr Banks flew to Wellington on Tuesday to attend Parliament, it was with one opponent, NZ First leader Winston Peters, seated at his side.
On the return trip last night, Mr Banks found himself confronted by not one foe - but two. His seat was directly across the aisle from Mr Mallard, and Mr Peters was sitting in the row behind.