"If people see the original documents themselves it will give people reassurance."
Mr Hager said he wouldn't release all of the documents because some of them were of a personal nature.
"A lot of it doesn't actually reach the standard of public interest where there actually is a right to use it," he said.
He said he would be consulting with his source today.
Collins: It's an 'utter lie'
Judith Collins told Newstalk ZB this morning that the allegations the book makes that she assisted a prisoner transfer for Mr Slater was an "utter lie... absolutely, completely false."
She said "pretty much" all allegations about her in the book were lies.
Mr Hager's book - based on thousands of messages between Mr Slater, National Party spin doctor Jason Ede and others - claims Mr Ede ran Mr Key's dirty tricks operations which were kept at arms' length from the Prime Minister to avoid damaging his image.
One of the allegations is that Mr Ede covertly accessed the Labour Party's computer systems in mid-2011.
Mr Key yesterday told reporters in Dunedin yesterday that Mr Ede was not involved.
Farrar: I've been hacked or spied on'
National Party pollster and blogger, David Farrar, has this morning announced he has been hacked or spied on.
In a post on his blog, Kiwiblog, Farrar said that footnotes in Nicky Hager's book, Dirty Politics, contained information that could not have come any other way.
"To my shock I realised that Hager had info in the book that could not have come from the hacking of Cameron Slater, but could only have come from my computer, my apartment or my office."
He says copies of two scripts used by his company, Curia Research, could not have come from Cameron Slater's computer systems as no-one else had them.
"The two most likely scenarios are that my computer systems have also been hacked, or that someone physically removed the scripts from my office (or possibly apartment). All of these scenarios make me feel sick, and make me worry about the security of the 100+ staff working for me."
He said that the intrusion had made him consider giving up politics, "but I'm not going to do that in haste."
