A 30-page memorandum sent to Downing Street by Eurosceptic Conservative MPs sets out in forensic detail why they believe a customs partnership with the EU is “undeliverable”.

The 60-strong European Research Group, led by Jacob Rees-Mogg, wants Theresa May to rule out a customs partnership.

The Prime Minister is meeting her Brexit “war Cabinet” on Wednesday to discuss what Britain’s post-Brexit customs arrangement with the EU should be.

The ERG insists the Government must stick with a “highly streamlined” customs arrangement, which would use technological solutions and trusted trader status schemes to solve the issue of the Irish border.

The document says that a customs partnership would make an independent trade policy a “practical impossibility”.