London - Britain's Brexit Minister David Davis has come under fire after admitting to MPs that the government did not have a sector-by-sector "impact assessment" for leaving the European Union.

Davis told the House of Commons Brexit committee that "he wasn't a fan of economic models because they have all proven wrong," citing the 2008 economic crisis as an example of their inability to model "paradigm" changes.

The government initially said it would provide the committee with a 850-page assessment of Brexit's impact on 58 economic sectors. However, Davis, on Wednesday, said the studies were merely "sectoral analyses", which did not predict the effects of leaving the EU.

The fact that no impact studies had been done for aviation, automobiles and financial services drew derision.

"On the most fundamental change that we are facing as a country you've just told us that the government hasn't undertaken any impact assessments at all," said commission chair Hilary Benn.

Davis said there would be such studies "at some stage" when Brexit negotiations move on to the second phase, but other lawmakers also hit out.

"Davis is either grossly incompetent, or someone who struggles with the truth and treats MPs with contempt," said Green Party co-leader Caroline Lucas. "Either way, he should be out of his job."

Former Liberal Democrat leader Tim Farron also called for Davis to step down, writing on Twitter that under his leadership "the Brexit department has turned incompetence into an art form."

MPs have also approached House of Commons speaker John Bercow about the possibility of a contempt motion against Davis, but the move appears unlikely after the committee voted it down by 11 members to 8.