Dutch EU vice president Frans Timmermans has told the BBC British ministers were ‘running around like idiots’ when they first arrived in Brussels to negotiate Brexit in 2017 and that they were shockingly unprepared.

‘We thought they are so brilliant,’ Timmermans told the Panorama programme, in an interview recorded in March. ‘That in some vault somewhere in Westminster there will be a Harry Potter-like book with all the tricks and all the things in it to do.’

However after seeing the then-Brexit Secretary David Davis speaking in public, Timmermans said he changed his mind. ‘I thought, “Oh my God, they haven’t got a plan, they haven’t got a plan”.’ Timmermans said.

‘Time’s running out and you don’t have a plan. It’s like Lance Corporal Jones, you know, “Don’t panic, don’t panic!” Running around like idiots,’ he said, in a reference to the Dad’s Army television comedy show.

Asked about Boris Johnson’s approach to the Brexit negotiations when they began, Timmermans said: ‘Perhaps I am being a bit harsh, but it is about time we became a bit harsh. I am not sure he was being genuine.’

‘I have always had the impression he is playing games.’ Johnson is tipped to become the next prime minister of Britain and has said he will ensure Brexit takes place by October 31.

The Panorama programme ‘Britain’s Brexit Crisis’ will be broadcast on Thursday at 10pm Dutch time.