LONDON, United Kingdom (AFP) — British Foreign Secretary Boris Johnson on Tuesday dismissed as “crazy” a government proposal for customs arrangements with the EU after Brexit, forcing cabinet divisions into the open once again.

Johnson, an outspoken supporter of Britain’s withdrawal from the European Union, said the plan backed by Prime Minister Theresa May would not fulfil many of the promises of Brexit.

“If you have the new customs partnership, you have a crazy system whereby you end up collecting the tariffs on behalf of the EU at the UK frontier,” he told the Daily Mail.

He added: “If the EU decides to impose punitive tariffs on something the UK wants to bring in cheaply there’s nothing you can do.”

Citing the pledges of the Brexit campaign, Johnson said: “That’s not taking back control of your trade policy, it’s not taking back control of your laws, it’s not taking back control of your borders.”

Last year, London put forward two options to ease cross-border trade with the EU but, with Brexit looming in March 2019, has still yet to make a final decision on which to pursue.

May’s preferred option, the customs partnership, was reportedly rejected at meeting of her senior ministers last week, while Brussels has also condemned it as “magical thinking”.

Downing Street insisted both proposals are still “viable”, even if they are now subject to revision.

“Following last week’s cabinet sub-committee meeting it was agreed that there are unresolved issues in relation to both models and that further work is needed,” May’s spokesman said.

“The prime minister asked officials to take forward that work as a priority.”

Lords rebellions

A customs partnership model would involve Britain collecting EU tariffs on goods heading into the bloc but charging its own on UK-destined products.

Aside from Johnson, the untested proposal has also been criticised by up to 60 eurosceptic members of May’s Conservative party.

A second option, “maximum facilitation”, would involve using technology to minimise customs checks, but the EU has also cast doubt on its viability.

A decision is not expected for at least another week, but the clock is ticking ahead of a crucial EU summit in June.

There are also concerns that neither option will now be ready for when Britain leaves the bloc’s customs union at the end of the Brexit transition period in December 2020.

The prime minister has promised to leave the customs union and single market to allow Britain to forge its own trade policy and control immigration.

But there are fears of the economic impact of such a clean break with its closest trading partner, as well as concerns about the risk to the fragile peace in Northern Ireland of imposing border checks with EU-member Ireland.

Some pro-Europeans believe the only solution is to maintain existing trade ties, and the House of Lords will later Tuesday debate amendments seeking to keep Britain’s access to the single market. It is unclear whether the changes would pass, however, as the main opposition Labour is asking its members to abstain in any vote.

The unelected Lords have inflicted a string of defeats on the government during the passage of the EU (Withdrawal) Bill, which sets the legal framework for Brexit.

Two other amendments put by Labour are likely to pass later, including one that would remove the March 29, 2019 date of Brexit from the face of the bill.