Dirty Politics author Nicky Hager does not believe National Party advisor Jason Ede - named in the book as John Key's "black ops man" - has resigned voluntarily.
The prime minister said Mr Ede had resigned after 11 years with the party because he wanted to do something different. He resigned last Friday, effective immediately.
Dirty Politics accused Mr Ede of feeding information to the Whale Oil blogger Cameron Slater and accessing confidential records from a Labour Party database. It described him as Mr Key's "black ops man".
Mr Key said he did not agree with how Mr Ede was characterised in Dirty Politics and had not suggested he leave.
Blogger David Farrar said Mr Ede resigned voluntarily, not because of allegations in the book.
"With all the intense spotlight on him and 11 years there, he would rather move into a quieter role in the future," he said.
"From the Government's point of view, they've never wanted a focus on the allegations in the Hager book, so there's no difference there pre or post election."
But Mr Hager rejected Mr Farrar's explanation.
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"Jason Ede disappeared during the last five-and-a-half weeks of the election campaign but it's pretty obvious that he was given a free holiday or something to get him out of the way, and then he was resigned out of a job rather than facing up to the issues," he said.
"But I think there's a connection between being caught out so comprehensively and his sudden departure."
Mr Ede could not be reached for a response and Whale Oil blogger Cameron Slater refused to comment.