Boris Johnson held up a wrapped kipper to illustrate his argument about “pointless” EU rules at the final Tory leadership hustings in London yesterday

A no-deal Brexit would blow a £30 billion annual hole in the public purse as the economy shrinks and tax receipts collapse, driving the national debt above £2 trillion for the first time, the government’s budget watchdog has warned.

Using the International Monetary Fund’s least-worst scenario of the impact of a no-deal and no-transition Brexit on October 31, the Office for Budget Responsibility said that the government would have to borrow roughly an extra £30 billion for each of the next four years, loading an extra £272 billion to the national debt by 2024.

If a deal is struck there would be room to borrow more than has been planned. The government could borrow an extra £25 billion a year and still keep debt falling