Dirty Politics author Nicky Hager has been taken to court by police in an attempt to access the source material used in his book.

Earlier this month police conducted a 10-hour search of Hager's house, during which he said computers and papers were seized in what appeared to be an attempt to discover the identity of the person who provided information used in the book.

The book was an election bombshell based on hacked email and social media material belonging to WhaleOil blogger Cameron Slater.

Yesterday at the High Court at Auckland, police asked Justice Geoffrey Venning to let them review the documents taken in the raid, after Hager claimed legal privilege to protect his sources under the Evidence Act.


Hager's lawyer, Felix Geiringer told Radio New Zealand that his client would also be challenging the legality of the search warrant police used to raid Hager's home.

It was being challenged on three fronts, RNZ reported, the legality of the decision by police to apply for the search warrant, the granting of the warrant by a judge and the execution of the warrant by police.

Mr Geiringer told RNZ that police were looking for information that would lead them to the identity of the hacker dubbed Rawshark.

"Rawshark is a confidential source of Mr Hager.

Mr Hager's given him an assurance of confidentiality and the law says that when a journalist does that, that information that identifies that person is privileged," Mr Geiringer said.

"The first issue is that it appears that the very thing that the police are looking for is protected by journalistic privilege.

"In order to try and find the information about this Rawshark, what the police want to do is look through all of Mr Hager's material and in particular, they want to examine anything in Mr Hager's possession that indicates information about a potential confidential source.

"In fact, what the police want to do is they want to examine all of Mr Hager's sources for all of his research."

Doing so would override the privilege awarded to all of Hager's sources, which would have an enormous impact on his ability to act as an investigative journalist, Mr Geiringer said.

"I would suggest that it has an enormous impact on the ability of every journalist in New Zealand to do their work."

A campaign to help with Hager's legal fees has raised more than $57,000.