Labour Leader Andrew Little believes the Prime Minister is feeling "a little bit sensitive" because not all New Zealanders have rushed to rally behind his decision to send troops to Iraq.
John Key has been under intense pressure since last week's decision to send more than 100 non-combat New Zealand soldiers to the Middle East in order to help Iraq in its fight against the terrorist group Islamic State.
Mr Key says we can't stand by and do nothing as innocent people are butchered by the militants, arguing also the group poses a threat to New Zealand.
However, Mr Little believes there is still a case to be made about why we are putting our own troops in possible danger in order to "prop up" the Iraqi army.
"I think there are still a lot of New Zealanders who need to be convinced that this is the right thing to do," he told TV ONE's Breakfast.
Mr Little said Labour won't criticise the soldiers who are sent up there.
"They've got a job to do, they'll be professional," says Mr Little.
"They'll be at great risk and of course our hearts go out to them to make sure they can do their job."
However, he says Labour will remain critical of the decision to deploy troops instead of providing other aid.
"I cannot see any strategic sense in it," he said.
New Zealand soldiers will be deployed to Iraq in May.