The Foreign Minister has delivered a sharp rebuke to the United Nations Security Council, saying it is failing to do its job particularly when it comes to preventing conflict.
Mr McCully made his comments in a speech to the Security Council open debate in New York.
A major plank of New Zealand's bid for a place on the Security Council was reform of the way it operates, and Mr McCully told the Council it should listen to smaller members of the UN, and take heed of their disappointment and frustration.
"The Council is charged with responding to threats to international peace and security. Yet in relation to too many of those current threats, the Council has dealt itself out of its proper role.
"Where it is involved, it has often been too late."
Mr McCully told the Council it has a completely inadequate focus on conflict prevention, and far too much emphasis on peacekeeping.
He said the use of the veto, that can be wielded by any of the five permanent members, often renders the Council impotent in the face of many international conflicts.
"The use of the veto, or the threat of the veto, is the single largest cause of the UN Security Council being rendered impotent in the face of too many serious international conflicts.
"Whether we are talking about Syria or the Middle East peace process, the veto's impact today far exceeds that which was envisaged in the UN Charter - to the huge detriment of the Council's effectiveness and credibility.
"We congratulate France on its initiative on the voluntary retirement of the veto in cases of mass atrocities."
He also says the Council fails to take pre-emptive action, opting instead to send in peacekeepers, after the fact.
"There is something wrong when we are spending over $8 billion per year on peacekeeping, but virtually nothing on the responsibility to prevent situations escalating into intractable conflict."
And he criticised the the Council for sending peace keepers into dangerous environments without adequate mandates or resources.
Mr McCully urged the Council to have a serious look at where it is failing, and improve its performance as it celebrates its 70th anniversary.