The Brussels representatives of some of the largest FTSE 100 companies are finding that calls go unreturned, discussion papers are not shared and invitations to key meetings are no longer extended. One source said: “We’re finding now that nobody will take our calls. Britain is still a member state but we can’t get a hearing.”

Another experienced Brussels operator at one of Britain’s biggest global players said UK officials inside the European Commission were also being excluded, making it doubly difficult to hold any sway.

He said: “The single most disturbing thing is what’s happening within the arms of the British government based here. Those individuals who were amenable to business are either being side-lined or nudged out of key roles.