One of Britain's most authoritative judicial figures last night delivered a blistering attack on the invasion of Iraq, describing it as a serious violation of international law, and accusing Britain and the US of acting like a "world vigilante". 

Lord Bingham, in his first major speech since retiring as the senior law lord, rejected the then attorney general's defence of the 2003 invasion as fundamentally flawed. 

Contradicting head-on Lord Goldsmith's advice that the invasion was lawful, Bingham stated: "It was not plain that Iraq had failed to comply in a manner justifying resort to force and there were no strong factual grounds or hard evidence to show that it had." 

Adding his weight to the body of international legal opinion opposed to the invasion, Bingham said that to argue, as the British government had done, that Britain and the US could unilaterally decide that Iraq had broken UN resolutions "passes belief". 

Addressing the British Institute of International and Comparative Law last night, Bingham said: "If I am right that the invasion of Iraq by the US, the UK, and some other states was unauthorised by the security council there was, of course, a serious violation of international law and the rule of law.  

The moment a state treated the rules of international law as binding on others but not on itself, the compact on which the law rested was broken, Bingham argued. Quoting a comment made by a leading academic lawyer, he added: "It is, as has been said, 'the difference between the role of world policeman and world vigilante'." 

Top Judge: US & UK Acted As 'vigilantes' In Iraq invasion