The United Nations has the power to punish Putin. This is how it can be done | Simon Tisdall

Ukraine urgently needs help - and if the organisation can't act effectively now, the global consequences could be catastrophic

President Volodymyr Zelenskiy's address to the UN security council came at a crucial moment for the United Nations as well as Ukraine. Russia's illegal war of aggression, and the collective failure of the other 192 member states to stop it, represents the biggest crisis for the UN since Iraq in 2003. This visceral threat to the organisation's authority - practical, legal and moral - is one from which it may not recover.

The principles enshrined in the 1945 UN founding charter, primarily aimed at upholding peace between sovereign states, have been torn up by the Kremlin. Repeated pleas by the UN secretary general, Antonio Guterres, for an immediate end to hostilities are ignored. And the humanitarian laws of war are being brutally disregarded, as the multiple crimes committed in Bucha, Mariupol and across Ukraine show.

Simon Tisdall is a foreign affairs commentator. He has been a foreign leader writer, foreign editor and US editor for the Guardian