The $2bn (£1.5bn) a day that Donald Trump was spending on his reckless war in Iran could have funded saving more than 87 million lives, the head of the UN’s humanitarian agency, Tom Fletcher, said on Monday.

He also warned the normalisation of violent language, such as threatening to bomb Iran back to the stone ages, was very dangerous since it encourages every “wannabe autocrat” to use similar threats and tactics, including the destruction of civilians and civilian infrastructure.

Speaking at Chatham House in London, Fletcher, a former UK diplomat and adviser on foreign policy to successive prime ministers, also accused British politicians of forming a circular firing squad for more than 10 years which has left the UK in a “defensive crouch”.