John Banks has been interviewed by police as they investigate the "teapot tape" recording which caused a sensation during the election campaign.
The ACT MP confirmed on Monday he had been interviewed about his conversation with Prime Minister John Key but wouldn't discuss details.
Mr Key says he hasn't been interviewed and his only contact with the police was when he laid a complaint over the way the recording was obtained.
He believes freelance cameraman Brad Ambrose deliberately left a recorder running on the table in the Auckland cafe where he met Mr Banks to show his support for ACT's Epsom candidate.
Ambrose says it was inadvertent, but he gave the recording to the Herald on Sunday newspaper and TV3.
Neither organisation published it but New Zealand First leader Winston Peters gained significant media attention during the campaign by releasing parts of it.
Police have to decide whether the conversation was private and whether to charge Ambrose with an offence.
NZN