Philip Hammond's Brexit transition plan has come under public attack from Boris Johnson’s economic guru, as significant Tory splits begin to emerge.

Gerard Lyons, the leading City economist, criticises the Chancellor for exploiting Theresa May’s absence on holiday to publicise his own Brexit views.

Writing for the Telegraph, Mr Lyons demands that any transition phase is just two years long – a year shorter than outlined by Mr Hammond.

And he compares warnings of a Brexit “cliff-edge” for businesses to hysteria over the Millennium Bug, which never came to pass.

“There is alarmist talk of a cliff-edge,” he writes. “It reminds me of the Y2K bug where computers were apparently going to stop at the millennium.”