Philip Hammond has warned the UK will not be able to control key elements of a no-deal Brexit.
The chancellor told BBC Panorama that if the UK leaves without a deal, then the EU will control many of the levers – including what happens at the French port of Calais.
Ex Brexit Secretary David Davis told the programme that Whitehall never believed a no-deal Brexit would happen.
The EU has set the UK a deadline of 31 October to leave the bloc.
But despite spending £4.2bn on Brexit preparations, Hammond warned that the government has limited influence on how a no-deal scenario might look.