Prime Minister John Key says his former adviser and National Party staffer Jason Ede was not forced out of his job in response to the Dirty Politics scandal.
But the book's author Nicky Hager said it was clear Mr Ede could not stay with National given allegations made about his role in feeding information to right-wing bloggers such as Cameron Slater. "Just like Judith Collins, it was inevitable Ede would have to go because of the things he had been caught out being involved in."
The National Party confirmed that Mr Ede resigned on Friday from his job at the party's Wellington office.
National's general secretary Greg Hamilton said in a statement: "Along with the Prime Minister and his office, we thank Jason for his 11 years of service to the National Party and wish him well for his future."
Mr Key told TV3 that his former media adviser was not pushed: "He genuinely wanted to move on, but I think he made the right call."