Cabinet Minister Judith Collins says Nicky Hager's allegation that she leaked privileged information to the right-wing blogger Cameron Slater is a lie.
Mr Slater earlier confirmed that Ms Collins gave him the name of a public servant who he then said was the source of a leak to the Labour Party.
Mr Hager's book, Dirty Politics, outlines how Mr Slater publicly accused the public servant, Simon Pleasants, of providing the leak.
The leak had allowed Labour MPs to question Bill English in Parliament about his accommodation allowance in 2009.
Mr English was getting $700 in taxpayer funding a week for his house in Karori.
Mr Slater told TV3's The Nation that he did receive an email from Ms Collins identifying Mr Pleasants and his position but said he could not remember the conversation which led to the email.
"I'm not sure whether you'd call it a leak," he said. "I've certainly had a discussion about a name of a person from what I understand around that - Simon Pleasants of course being a former Labour Party staffer."
The minister said it was common knowledge that the person worked for Ministerial Services.
Mr Pleasants' employer, the Department of Internal Affairs, said he had made it clear that he did not leak the information in question and had never leaked anything.