Boris Johnson
Britain's Foreign Secretary Boris Johnson leaves after voting in local government elections in London, May 3, 2018. REUTERS/Hannah McKay

British Foreign Secretary Boris Johnson has attacked Prime Minister Theresa May's plan for a customs partnership with the European Union after the U.K. leaves the bloc — the latest outbreak of discord within the government over Brexit.

Johnson told Tuesday's edition of the Daily Mail newspaper that the partnership idea was "crazy" and would create a "whole new web of bureaucracy."

The comments come after May's Cabinet last week failed to agree on a proposal for Britain's future customs relationship with the EU. May's preferred option is a partnership under which the U.K. would collect import duties on behalf of the EU for goods arriving at British ports.

Johnson said May's idea was "totally untried and would make it very, very difficult to do free trade deals."

His dismissal of the proposal stands in marked contrast to comments by Business Secretary Greg Clark on Sunday that the customs partnership option was still being considered by the government.

May's Cabinet is split between ministers including Johnson who favor a clean-break "hard Brexit," which would leave Britain freer to strike new trade deals around the world, and those including Chancellor of the Exchequer Philip Hammond who want to keep closely aligned to the EU, Britain's biggest trading partner.

The two sides remain at loggerheads, almost two years after Britain voted to leave the EU and less than a year before it officially exits the bloc on March 29, 2019.

That has led May, who heads an unstable minority government, to put off taking a firm stand on key Brexit issues for as long as possible — to the frustration of EU leaders, who have warned repeatedly that time is running short to strike a deal.