Labour Party leader Phil Goff says John Key could have cleared up the issue of his cafe conversation with John Banks a week ago if he had just come clean.
The meeting was widely viewed as a signal to National supporters that they should vote for Mr Banks, ACT's candidate for Epsom, on election day.
The conversation between Mr Key and Mr Banks on 11 November was recorded by freelance cameraman Bradley Ambrose and given to the Herald on Sunday newspaper.
Police are investigating a complaint laid by John Key, who says the conversation was private and recorded illegally.
Mr Ambrose's lawyers asked Justice Winkelmann in the Auckland High Court on Tuesday to declare that the conversation was not private, because the politicians staged the media event. The judge has reserved her decision until Wednesday.
Phil Goff says if John Key said something insulting about people on the tapes, he should just apologise and move on.
However, he won't say whether he believes the tapes should be released.
"It would clear the matter up, but that's a matter for the court to decide, or for the Prime Minister just to come clean on. I'll leave it up to the courts."
Mr Goff believes the whole matter is political and a waste of police time.
John Key was campaigning in the South Island on Tuesday.
Police have indicated they will wait for the court's judgement before executing search warrants on four media organisations in their investigation into the recording. They are Radio New Zealand, APN, which owns the Herald on Sunday, TV 3 and Television New Zealand.