Scilly's MP Derek Thomas was one of 62 Conservative backbenchers to sign a controversial letter to Theresa May yesterday.
The letter from the European Research Group (ERG) made a series of suggestions, saying the UK should have "full regulatory autonomy" and be able to sign trade deals with other countries as soon as it leaves the EU.
The letter is seen as an ultimatum to the Prime Minister, with fellow Conservative MP Nicky Morgan describing it as a "ransom note".
Theresa May is struggling to meet the competing demands of Tory 'hard' Brexit supporters and former Remainers or backers of a 'soft' Brexit.
She will meet with senior ministers, dubbed the “Brexit war cabinet”, at Chequers tomorrow to decide on the UK's approach to the upcoming negotiations with the EU.
The 62 signatories of the ERG letter include former Conservative leader Iain Duncan Smith and high-profile MPs Jacob Rees-Mogg and John Redwood. The number is well over the 48 required to trigger a leadership contest if they are unhappy with the way the government is handling Brexit.
The Isles of Scilly voted to remain in the EU in last year's referendum by 56.4% to 43.6%.