The war against cannabis has been "comprehensively and irreversibly lost", former Conservative leader William Hague has said, as he urges Theresa May to legalise the drug.

Writing in the Telegraph Lord Hague says Mrs May should be "bold" and introduce a "major change" in policy, warning it is "deluded" to think cannabis can be "driven off the streets".

His intervention comes as the Prime Minister faces a growing Cabinet row over whether to allow medicinal use of the drug following pleas from the mother of 12 year-old Billy Caldwell.

Two of her most senior ministers - Sajid Javid and Jeremy Hunt - are understood to be pushing for a review of cannabis use but the Prime Minister is said to have blocked the discussion at a Cabinet meeting yesterday.

But in his column, Lord Hague says the PM should go further and imitate Canada, which is on the verge of legalising the drug for recreational use, writing: " Can British Conservatives be as bold as Canadian Liberals? We ought to be."

Lord Hague led the Conservatives from 1997 to 2001 during which time he advocated a "zero tolerance" stance on the drug.