A senior Labour MP is questioning the Serious Fraud Office's powers to move in on the media and says he tried, without success, to persuade the government to intervene.
Shadow attorney-general David Parker has revealed he wrote to Justice Minister Simon Power more than a year ago and received a reply on November 25 this year - the day before the election.
"Putting aside the remarkable coincidence that Mr Power finally addressed my concerns with a letter guaranteed not to make the media, I am seriously worried that National will continue to show scant respect for media freedom," he says.
"While I am relatively satisfied that there are sufficient protections for a free media in terms of protecting sources in most situations, that doesn't apply to the Serious Fraud Office."
Mr Parker wrote to Mr Power about the "disturbing case" in which the National Business Review was forced to hand over material to the SFO relating to the failed company South Canterbury Finance.
"No one is suggesting that the media should be able to obstruct justice but the SFO should not be above normal law," he said.
"Mr Power has seen fit to resist and the SFO will continue to be virtually a law to itself."
In his reply, Mr Power says the media cannot be required to provide a document or answer questions that reveal a source unless a court has ruled that it must.
He says changing the law would give the media greater protection than other sectors that deal with highly confidential and privileged information, such as lawyers, doctors and clergy.
Mr Power says he consulted Police Minister Judith Collins, who is responsible for the SFO, and she said it considered any change would impact on its wider operations.
Mr Power has quit politics and will hand in his ministerial warrant when a new cabinet is appointed.
He told Mr Parker "I trust my successor will engage constructively with you on these issues".
NZN