A lawyer for Dirty Politics author Nicky Hager has filed papers in the High Court challenging the legality of the police search of his client's home.
The police searched Mr Hager's Wellington home earlier this month and took away documents and devices.
They seized the material in a bid to identify the hacker known as Rawshark, a key source of Mr Hager's book.
However, lawyer Felix Geiringer is challenging the legality of the search warrant, the granting of it by a judge and the execution of it by the police.
Police officers have not yet examined the seized devices, which have been secured by the High Court.
Last week the police sought a High Court judge's permission to examine them.
Meanwhile, Prime Minister John Key said he believed he knew Rawshark's identity but did not plan to pass it on to the police.
Mr Key said a member of the public called him during the election campaign to reveal the identity of the hacker known as Rawshark.
"Someone rang me up - a member of the public - and said, look, they were pretty sure this was the name...
"In the end, it's of really no great consequence to me. I've moved on. I think 99 percent of the New Zealand public's moved on."
Mr Key said he could not be absolutely sure it was the right person and it was up to the police if they wanted to take the matter further.
"If the individual who told me wants to tell the police, they're welcome to go and do that. They know who they are and they may or may not."
Mr Key said he had learned since the teapot tape scandal in 2011 not to fret over such incidents.
"I've just come to realise it's par for the course in modern day politics in New Zealand that people will stoop to these kinds of levels... frankly it's not very pleasant, it's not very nice... but there's very little I can do about it."