Prime Minister John Key has addressed world leaders at the UN General Assembly in New York, calling on the Security Council to "do its duty".

Photo: SUPPLIED / United Nations

As part of New Zealand's statement in the general debate, Mr Key told leaders the Security Council had failed to act and it was now time for it to "step up".

"It's time for it to stop talking about what's right and do what's right. It's time for the council to do the job for which it was created," he said.

Mr Key said conflicts in countries such as Syria, Yemen and South Sudan showed how far the UN was from achieving the aspirations of its founders.

He warned of the "consequences of inaction" when it came to Syria.

"We cannot ignore the huddled travellers in the railway stations of Europe, or the reality of refugees scratching out a meagre existence in camps or makeshift homes in Turkey, Jordan and Lebanon," he said.

The Prime Minister also raised concerns about council members' right to veto.

"It is still our view that the veto is a constraint on the effectiveness of the council and realising the aspirations of the United Nations' members."

Mr Key finished by saying he was proud of the contribution New Zealand was making to the council but was "dispirited" by the council's failure to help the people of Syria and other countries.

"The collective effort of the Security Council, supported by the wider membership, could make a real difference.

"I think all of us who have been here over the past week know that collective action must start somewhere."

He last attended the UN leaders' week in 2013 and this is his first time since New Zealand was elected to the Security Council.