At least a dozen members of Theresa May’s Cabinet are lining up to block her plans for a new “customs partnership” with the European Union, The Telegraph can disclose.

Two pro-Remain ministers say they were among a growing number of figures around the Cabinet table who opposed the proposals described by Boris Johnson, the Foreign Secretary, as “crazy”.

The Telegraph has now established that 12 out of a total of 28 individuals who sit in Cabinet alongside Mrs May oppose her favoured plans for Britain’s post-Brexit customs relationship with the EU. However, government sources believe the total could be as high as 15.

The disclosure, which is likely to unnerve the Prime Minister and Julian Smith, her Chief Whip, comes after Sajid Javid, the Home Secretary, and Gavin Williamson, the Defence Secretary, became the first Remain voters to switch sides to join Brexiteer opposition to the plans, in a meeting of the Cabinet’s Brexit sub-committee.