The opposition's demanding to know if the tobacco industry is behind the documents the Associate Health Minister sent to officials suggesting a freeze on tobacco tax.
Casey Costello has been under increasing pressure since she told RNZ she had not specifically sought advice on freezing the tax, when she had.
The papers also say that nicotine is as harmful as caffeine and that the tobacco industry is on its knees.
The Minister won't say who wrote the documents, and Labour is calling for her to resign.
She declined to come on the programme.
RNZ investigative journalist Guyon Espiner spoke to Corin Dann.