Prime Minister John Key has used a speech to the United Nations to launch a scathing attack on the Security Council, warning that inaction over events like the humanitarian crisis in Syria had damaged its credibility.



In notes for a trenchant speech lasting nearly 20 minutes, Key said the UN was in urgent need of reform - a key pitch in New Zealand's bid for a seat on the Security Council.



"Its key organs, particularly the Security Council, have become hostage to their own traditions and to the interests of the most powerful," Key said.



"We now seem to have a practice whereby the permanent members can not only block council actions through the veto. They also appear to have privileged access to information and can stop the council from meeting if it does not suit their collective purposes.



"Such behaviour damages the reputation and credibility of the wider organisation and must be challenged."



The speech was delivered as the Security Council thrashed out a deal for Syria to surrender its chemical weapons stockpile.



It was reported today to have made a breakthrough by reaching agreement on a "binding and enforceable" draft resolution between the five permanent members. The council will meet tonight over the resolution. But it has been criticised over its failure to act sooner in response to the two and a half-year crisis.



Key described the situation in Syria as a "brutal reminder" of the big gap between aspiration and delivery by the UN.



But it was not just a failure of the UN - it was a failure of states as well.



"There would be no dreadful humanitarian situation in Syria if Syria's leaders had upheld the commitments made to the international community and to the Syrian people when Syria joined this organisation and ratified the Human Rights Covenants," he said.



But Key also indirectly criticised Russia, which previously blocked action against Syria.



"This organisation would not also have been a powerless bystander to the Syrian tragedy for over two years if the lack of agreement among the Security Council's permanent members had not shielded the Assad regime - thereby re-confirming the fears of New Zealand and others who had opposed the veto at the original San Francisco conference in 1945," Key said.



The UN had confirmed "unequivocally and objectively" that chemical weapons had been used in Syria.



Its report found "clear and convincing evidence that surface-to-surface rockets containing the nerve agent sarin" were used on August 21.



"The information in the report also makes it very clear that those rockets must have been fired by the Syrian regime," Key said.



"As the secretary-general has said, these are war crimes. Those responsible must be bought to account," he said.



"Those that try to cast doubt on the report's conclusions make themselves look foolish and do a disservice to the UN."



It was imperative the Security Council now acted and it must adopt a resolution that responds to the use of chemical weapons, the prime minister said.



"It must find a means to hold those responsible to account and establish an effective mechanism for the destruction of those weapons in line with the proposal developed by the United States and Russia.



"The resolution must also provide for the protection of the civilian population."



Key has been in New York drumming up support for New Zealand's Security Council seat bid.



He said New Zealand was not advocating revolution "but we are asserting the council can and must do better in the way it conducts its business.



"That is the approach New Zealand will bring to the Security Council if we are elected next October," he said.



"From the 1950s to the 1990s we could blame the Cold War when the Security Council did not act.



That does not wash today."



Key called this week for permanent Security Council members to be stripped of their right of veto over acts of genocide or war crimes.

GLOBAL STAGE: Prime Minister John Key addressing the UN General Assembly in New York.