Sixty Conservative members of the British Conservative think-tank, the "European Research Group" have sent a letter and 30-page report to Prime Minister Theresa May detailing their opposition to her reported plans for form a customs partnership with the European Union after the United Kingdom leaves the European Union.
In their letter, the so-called Hard Brexiteers of the Conservative Party outlined that they thought forming such a partnership with the Continental bloc would amount to retaining membership of the Customs Union itself, tying Britain also to the rules of the European Single Market which it will have no say in forming.
The warning, which arch-Hard Brexiteer Jacob Rees-Mogg on BBC Radio 4 denied was an ultimatum to the PM, is the latest in a string of interventions by elements of the Conservative Party, whose supporters overwhelmingly backed Brexit and who fear that Mrs May and figures such as Chancellor Philip Hammond may seek to dilute the degree of separation from Europe.
Continuing pressure from within her own party essentially forces the Prime Minister back to her original position, on which she was forced to compromise when the House of Lords voted April 18 to oppose her plan to fully withdraw the UK from the European Customs Union.
Mrs. May has previously received private letters from her own cabinet members, chiefly Boris Johnson and Michael Gove offering "advice" on pursuing a Hard Brexit with Europe, interpreted widely as an implicit threat to her leadership of the party.
The Prime Minister is today chairing a meeting of her cabinet in which leading pro-Brexit ministers such as International Trade Secretary Liam Fox, Foreign Secretary Boris Johnson and Brexit Secretary David Davis are expected to push for Mrs. May's attempted "middle-road" solution, which would involve developing a "hybrid" model-relationship with Brussels, to be abandoned.
A key objective of the hybrid model is to solve the question of avoiding a hard Irish border, which would eventuate were Britain to leave the Single Market and the Customs Union. The Republic of Ireland has made clear its intent to veto any Brussels-London agreement that doesn't rule out the possibility of customs posts forming along the Northern Irish frontier.