Police have decided not to lay charges against Radio Live for a programme hosted by the prime minister during the 2011 election campaign.
Police national manager of criminal investigations Detective Superintendent Rod Drew says there is insufficient evidence to prosecute.
John Key hosted the hour-long show on 30 September 2011.
He did not discuss politics and instead interviewed well-known people, including All Blacks' captain Richie McCaw and film-maker Sir Peter Jackson.
The Labour Party complained to the Electoral Commission, saying Radio Live had not afforded its leader, Phil Goff, the same opportunity.
The Commission referred the show to the police amid concerns it breached the Broadcasting Act.
Mr Drew says the decision not to lay charges followed a thorough investigation, that included the findings of the Broadcasting Standards Authority and the Electoral Commission, both of which had contrasting views on whether or not Mr Key was taking part in an election programme.
Labour Party deputy leader Grant Robertson says the party accepts the police decision but says it still believes the broadcast breached electoral law.
He says the election programme was a political stunt by the prime minister.