Leaving the European Union would not guarantee a rosy economic future for the UK, the international trade secretary Liam Fox has admitted.

In a frank assessment of Britain’s prospects Dr Fox said that fellow Brexiteers needed to beware of succumbing to “irrational positivity”.

He said that Brexit offered opportunities but the UK would still be subjected to “buffeting pressures in the global economy” that the government would not be able to control.

Dr Fox’s remarks will be seen as a rebuke to Boris Johnson, the former foreign secretary, who has talked repeatedly of a “glorious vision” for the future of a Britain free from interference from Brussels.

They also, however, reflect concerns among the Conservative right that post-Brexit Britain will be seeking economic growth from