UPDATED 6.33PM Prime Minister Bill English has been briefed on allegations in a new book about a New Zealand military operation in Afghanistan - and says "there doesn't appear to be anything new" in the claims.

English said the book's politically motivated and says from what he's heard so far an inquiry's not necessary.

On his way to question time at Parliament this afternoon English told media he had received an initial briefing from officials about claims in Nicky Hager and Jon Stephenson's book Hit & Run.

He would receive further written advice.

"What has become clear is they believe the inquiries that have already been conducted have covered the issues," English said.

"There doesn't appear to be anything new in these allegations and a lot of them are couched pretty conditionally even by the authors themselves."

Hager and Stephenson say our elite soldiers killed six civilians, and hurt 15 more in 2010.

They claim, in their book, it was a retaliatory attack targeting those the SAS believed responsible for the death of New Zealand soldier, Lieutenant Tim O'Donnell, who was killed by a roadside bomb less than three weeks earlier.

LISTEN: Nicky Hager speaks with Mike Hosking

Earlier today, Bill English wouldn't rule out an inquiry into the allegations, but said he won't be rushed into holding one.

• PM asked to hold formal inquiry into the SAS

English said the advice he'd had is that the Defence Force is standing by its statements, that it's unfounded.

He said he'd look into "whether there's anything new in the book, which looks at least partially politically motivated".

English said there's a whole range of assertions in the book launched last night.

Despite the fact John Key was in office during the raids, Mr English said he doesn't think it's appropriate to talk to him about the book.

"He's leaving politics and as the Prime Minister it's my role to take account of these matters."

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Labour leader Andrew Little said the book alleges the deaths were the result of a New Zealand mission and every New Zealander has a right to know the truth about what happened.

"It was New Zealand intelligence gathering, it was New Zealand mission planing and it was New Zealand soldiers involved in the mission so we are heavily involved in it and we do need to take an interest in what has happened and that should be reflected in an inquiry," he said.

"If there is not a serious response by the government through an independent inquiry then those allegations end up hanging around and could do damage to our reputation, and that would be wrong."

Labour will commit to an inquiry if elected in September, but Mr Little hopes it won't come to that believing there is nothing for Mr English or Defence Minister Gerry Brownlee to be ashamed or embarrassed about in calling an inquiry.

Green Party co-leader Metiria Turei said, politics aside, the government must investigate.

"If there is nothing to hide, then there is nothing stopping (Prime Minister) Bill English from announcing a full, independent inquiry into those allegations today," she said.

"Full transparency from the government is the only way we're going to find out exactly what happened. Refusing to comment and refusing to investigate won't make these allegations go away."

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NZ First leader Winston Peters agrees, saying the integrity of the servicemen involved is being challenged and the allegations cannot be left to stand without a full inquiry.

"It's not good enough for the Prime Minister, Bill English, to say there has already been an inquiry by the Afghan government and Coalition forces," he said.

"What New Zealand must do is appoint a respected and trustworthy individual who the public can have faith in, and get an inquiry underway immediately."

Deputy leader Ron Mark said he has absolute confidence in the SAS and people he's spoken to assure him they operate to the highest ethical standards.

He said while his party wants an inquiry to go ahead it's more about ensuring the integrity of the SAS and Defence Force is maintained.

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The inquiry could be closed to allow SAS members to give evidence in confidence, he said.

The New Zealand Defence Force released a statement on Tuesday night standing by their 2011 position that an investigation concluded "that the allegations of civilian casualties were unfounded".

Additional reporting by NZN