Britain will be unable to leave the customs union before 2023, ministers have been told, leading to fears that the delay will be exploited by Remainers to thwart Brexit.

In a briefing to the Cabinet’s Brexit sub-committee earlier this week, senior civil servants said highly complex new technology that will be needed to operate Britain’s borders after Brexit might not be ready for another five years.

Theresa May has asked officials to carry out more work on the two options currently being considered by the Government to replace the customs union – acustoms partnership and a so-called “maximum facilitation”.