The Red Cross says it is "surprised" over Prime Minister Jacinda Ardern's objection to the naming of kidnapped nurse Louisa Akavi.
Akavi was taken hostage by the Islamic State in 2013, while working for the Red Cross in Syria.
Successive governments have all agreed not to name her in case it was a threat to her safety.
On Monday, Akavi was named by the New York Times, and the International Committee of the Red Cross (ICRC) issued a plea for information regarding her whereabouts.
ICRC says the Islamic State has now lost the last of its territory, and they believe there is a good chance Akavi is alive.
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However, Ardern has remained tight-lipped about Akavi, saying she will not comment on the case, as it would be "preferable," for the case not to be in the public domain.
"Decisions have been taken that were not our own and I won't be commenting further on decisions made by others," she said on Monday.
However, ICRC director of operations Dominik Stillhart has defended the decision to name Akavi, and says he is "surprised" by the objection of Ardern.
"I am confident the decision was made in full transparency and coordination with the New Zealand Government," he said on Monday.
"When I woke up this morning, and I saw that that was the information that came out of New Zealand I was slightly surprised,"
He says every decision was made with Akavi in mind.
"Every decision, including this one, was to maximize the chances of winning Louisa's freedom," said Stillhart.
"We would not have made that decision without the support of the New Zealand Government."