Prime Minister John Key has been forced to defend sending troops to Iraq to train local forces following allegations of war crimes.

Photo: RNZ / Alexander Robertson

There have been reports that US-trained military units and Shiite militias are being investigated for possible war crimes, including the torture and execution of Sunni prisoners.

During question time in Parliament, Mr Key confirmed the Iraqi Government was investigating the allegations but said the New Zealand mission would not be put off.

More than 140 New Zealand Defence Force (NZDF) personnel are due to leave for Iraq in May to train soldiers in Taji, north of Baghdad.

Labour leader Andrew Little asked the Prime Minister whether he still stood by his decision.

"Does he still believe that people who oppose the deployment of New Zealand soldiers to train Iraqi Government forces need to get some guts and join the right side?

"In light of widespread evidence that Iraqi Government forces are committing war crimes?"

Photo: RNZ / Alexander Robertson

Mr Key said the right side was the international coalition of more than 60 countries who were campaigning against Islamic State (IS). He said IS was a brutal threat.

"I'm advised that the Iraqi Government is investigating allegations of abuses by Shiite militia and individuals with the Iraqi security forces," he said.

"We share the concerns of other partners about these allegations and we'll ensure our view is communicated to the Iraqi Government."

Mr Little said no one was arguing that IS was anything but evil.

He asked what the Government was doing to make sure that New Zealand soldiers would not be helping any Iraqi units that may have committed war crimes.

"How is it gutsy to force young New Zealanders to train an army guilty of many of the same crimes as IS?"

Mr Key said New Zealand would set the terms of the mission, including who would be trained, how they would be trained and when they would be trained.

But Mr Little asked for an assurance that New Zealand soldiers would not be helping Iraqi units that have committed war crimes.

Mr Key said the Iraqi forces must act consistently with the law.

He said the Government was committed to troops being in Iraq for two years.