On 29 November 2018 Dearlove co-signed an open letter, published in a British national newspaper, condemning Prime Minister Theresa May's negotiated Brexit withdrawal agreement after the 2016 Referendum on the issue, as the matter was passing through the House of Commons to be voted upon. In its text he stated that the Withdrawal Agreement as negotiated undermined MI6's nationally independent global intelligence power. In a published response, dated the same day, May's office issued a public rebuttal to the letter's content, singling out Dearlove personally from the named list of several signatories to the open letter, and stating that the Withdrawal Agreement "absolutely does not" compromise the national independence of the UK's intelligence capacity. In early December 2018 Dearlove, in a jointly authored text with Major-General Julian Thompson, published on the website 'Briefings for Brexit' an extensive reply to May's statement entitled 'The Prime Minister is misleading the country on defence and security', citing a 'worryingly poor understanding of the issues' by her office.