Theresa May’s former right hand man has revealed for the first time what went wrong in the general election campaign and what he believes the Conservatives must do to avoid defeat in five years’ time.

Nick Timothy, who resigned as the Prime Minister’s joint chief of staff in June, told The Daily Telegraph that the Tories lost their majority at the election because they abandoned Mrs May’s promise of change in favour of a “continuity” message.

He also admitted Downing Street was guilty of a breakdown in communications both with the public and with other Whitehall departments, leaving key policies vulnerable to attack.

In his first interview since leaving Number 10, the man dubbed Theresa May’s “brain” said she must find new ways to reform social care and forge ahead with intervention in “unfair” energy markets if she wants to hold off the challenge of Jeremy Corbyn.