The Defence Force's continued denial of the events described in Hit & Run is "bizarre", according to the authors.
Nicky Hager and Jon Stephenson's controversial book alleges six Afghan civilians were killed in an SAS 'revenge raid' in 2010, following the death of Lt Tim O'Donnell.
On Sunday night, the NZDF said Kiwi troops "never operated" in the villages described in the book, which is full of "major inaccuracies".
Prime Minister Bill English is siding with the Defence Force, telling The AM Show on Monday they were more likely to be right "than a story based on a number of unnamed sources".
"I have every reason to believe the Defence Force," he told host Duncan Garner. "I don't have any reason not to believe the Defence Force."
The Defence Force says the raids the SAS carried out were at a village a few kilometres away from those mentioned in Hit & Run.
Stephenson, also appearing on The AM Show, says he spoke to the villagers of Khak Khuday Dad and Naik on Sunday night, and they are "laughing" at the Defence Force's "embarrassing" denials.
"Is [NZDF Chief] Tim Keating really saying there were two raids using identical aircraft, in identical places with identical commandos, that left behind identical munitions in that one village, then a village two kilometres south? Seriously?"
Stephenson, who won a defamation case against the NZDF in 2015, says he's "100 percent" confident he and Hager will be vindicated.
"We have the top secret kill list they operated with... we have the evidence that they stormed those insurgents' houses... we have photos of the damage and we have testimony from a range of people - not only the villagers, but Afghan and SAS members who were on that raid."
Mr English, who last week wouldn't rule out an investigation into the claims, now appears to be doing just that.
"It appears that the allegations of war crimes don't need to be investigated," he said.
"The Defence Force was in one place, the allegations are made about villages a couple of kilometres away. That doesn't look like it requires investigation."
He says the actual SAS raid in question resulted in no casualties, despite not just the book but the Minister of Defence at the time - Wayne Mapp - who last week admitted the raid was a "fiasco".
Dr Mapp didn't deny the book's claims.
"One of the disasters of war is these terrible things can happen," he said.
Mr English says if the Defence Force carried out war crimes "it's on camera, it's on record".
"In the circumstance of the raid that actually happened, rather than the one that's written about in the book, no one has been able to establish that there were civilian casualties in that raid."
Stephenson says if Mr English doesn't call an inquiry into the claims, one will be "forced" upon him through the legal process.
"I'll stack my information up against Tim Keating any day of the week. I'll meet him any place, any time. He can either put up or shut up, as far as I'm concerned."