Foreign Affairs Minister Murray McCully has described Oxfam claims that New Zealand has contributed only $120,000 towards the Syria crisis as "wildly irresponsible and an insult to all New Zealanders".
Oxfam UK made the claims in a study arguing what countries should have donated based on their national income and overall wealth.
New Zealand came out bottom of the list of featured nations, with Oxfam saying it had committed just 1 per cent of what it should have - $120,000.
The study has been reported extensively in the UK, by outlets including the BBC and New Statesman.
Mr McCully said New Zealand had actually contributed $5.5 million over the past 16 months, supporting Syrian refugees in Turkey, Jordan and Lebanon, as well as those displaced in their homeland.
"For Oxfam to make claims that are so fundamentally incorrect challenges their credibility. Their claims are an insult to every New Zealander on whose behalf the Government has made $5.5 million in humanitarian contributions.
"These claims are even more outrageous coming from an overseas executive of an organisation whose New Zealand branch receives millions of dollars of taxpayer funding for partnership projects. I trust that Oxfam's New Zealand leadership take the trouble to correct their wayward colleague."
Oxfam NZ said the analysis of contributions to the crisis was based on the UN launching a US$5 billion appeal for Syria in June. "According to these calculations, New Zealand's fair share would be US$10.8 million (NZ$12.89 million)," said spokesman Jason Garman.
He acknowledged the analysis looked at bilateral funding only in certain areas and did not include aid the Government had contributed through other channels, such as the World Food Programme or the International Committee of the Red Cross.
But Mr Garman said Oxfam's information, sourced directly from the United Nations, was "incomplete, rather than incorrect".
"Oxfam acknowledges that through various channels, the New Zealand Government has contributed NZ$5.46 million towards a humanitarian response in Syria," he said.
"Our position is that internationally, New Zealand's reputation on this matter stands alongside the majority of the OECD countries, most of which have not met their fair share of contributions to this appeal."
According to the study only eight countries were giving sufficient funds. They included Kuwait, the UK, Luxembourg, Denmark, Saudi Arabia and Norway.
Head of the Oxfam Syria programme, Colette Fearon, said too many countries were not delivering the expected level of funds.
"While economic times are tough, we are facing the largest man-made humanitarian disaster in two decades and we have to seriously address it.
"The scale of this crisis is unprecedented and some countries must start to show their concerns to the crisis in Syria by putting their hands in their pockets. The situation demands committed funds in order to save lives."
More than two million people have fled Syria and registered as refugees. More than four million who remain need urgent assistance
In June, the UN launched a NZ$5.7 billion appeal for Syria, the largest in its history, but this remains just 44 per cent funded.
Funding gaps are already affecting the ability of organisations to respond to humanitarian needs and forcing them to make difficult decisions about how to use limited aid money.
Labour foreign affairs spokesman Phil Goff said it would be good if New Zealand could help out more.
"If we think times are tough in New Zealand, you've just got to see the situation facing the people over there. People have lost everything. In purely humanitarian terms, we need to do a bit more to try to make the plight of these people a little more tolerable."
Mr Garman said Oxfam NZ's Syria Appeal has so far raised just under $32,000 and encouraged New Zealanders to donate.