Police obtained detailed bank information about the journalist Nicky Hager without any court order while they were preparing to raid his house, court records show.
The search last October was part of a police investigation into the hacking of blogger Cameron Slater's computer.
Information from Mr Slater's computer was published in Mr Hager's book Dirty Politics.
Mr Hager challenged the legality of the search in a High Court hearing earlier this year.
The court has not yet released its decision, but court files released to the news website Scoop and published today show that police requested detailed information about Mr Hager from a range of organisations, without any court orders.
Those included Spark, Vodafone, Jetstar, Air New Zealand, TradeMe and "16 bank contacts".
The documents reveal that most of the organisations declined the request.
However, Westpac handed over detailed information, including bank statements.
The police can use a production order from the courts to force organisations to provide private information, if they have reasonable grounds to believe a crime has been committed, and if the documents would provide them with evidence of that crime.
In an affidavit, one of the police investigators, Detective Inspector Dave Lynch, said the request was to "ascertain any travel movements that may have been able to be linked to [Mr Hager] as well as assessing whether or not he was generating income from the proceeds of the book that could be considered for proceeds of crime action".
In a further affidavit, he said the request was also to work out whether Mr Hager had paid for any of the information from Mr Slater's computer.
However, in submissions to the court, Mr Hager's lawyers said the police request was unreasonable.
"The suggestion that the bank records might disclose payments to the source or otherwise disclose some other yet undetected offence was nothing more than speculation."
The police also lacked any reasonable grounds to believe that Mr Hager had even committed an offence, his lawyers said.
"This was done without obtaining any production orders and in circumstances where production orders would not have been available."