UK Prime Minister Theresa May PA Wire / PA Images PA Wire / PA Images / PA Images

THE HEAD OF the UK’s Revenue and Customs says that the plan to deal with Brexit advocated by hard-line Brexiteers within the government could cost Britain as much as £20 billion (€22.8 billion).

The so-called ‘Max Fac’ (which stands for maximum facilitation) plan which would see the issues surrounding border checks, such as in Northern Ireland, dealt with via technology and ‘trusted trader’ schemes, is advocated by Boris Johnson, Michael Gove, and Jacob Rees-Mogg.

Speaking before a Treasury select committee today, permanent secretary Jon Thompson said that Max Fac would prove to be substantially more expensive than the plan endorsed by prime minister Theresa May, a customs partnership model which would see the UK collect tariffs on behalf of the EU.

The £20 billion figure represents roughly twice what the UK currently contributes to the EU each year.

A spokesman for the government later told The Guardian in the wake of Thompson’s bombshell pronouncement that “work is ongoing” on both plans and “therefore any speculation about implementation is just that”.

With May’s cabinet bitterly split over the issue, the prime minister has been forced to split her ministers into two working groups in an attempt to end the impasse.

Thompson explained that the issue with the Max Fac solution is that it would force companies to draw up British customs declarations at a cost of £32.50 each.

“So you need to think about the highly streamlined customs arrangement costing businesses somewhere in the late teens of billions of pounds, somewhere between £17 billion and £20 billion,” he said.

Thompson also told Westminster’s dedicated Brexit committee today that Max Fac would not be ready before 2021 at the earliest.

Britain is due to officially exit the EU on 29 March 2019.