“An extension is expected to be forthcoming or a deal will have been secured, meaning that nobody will face the October 31 cliff edge.”
It comes as the country is braced for a snap election, with the prime minister set to compete for votes with Nigel Farage’s Brexit Party, whose core policy is a no-deal Brexit.
An election in either November and early December has been suggested as Johnson is set to face a vote of no-confidence if, as seems likely, he fails to get his new domestic agenda through parliament on October 15.
The letter adds that the campaign may have been “shaped by party political considerations” from the outset, amid reports that Vote Leave’s famous ‘Take Back Control’ slogan was rejected as its original title.
The letter reads: “I do not believe there can be any justification for spending £100m of public money disseminating information that is no longer factual, no longer anything other than nakedly partisan, and no longer the policy of any government that intends to operate within the law.
“Whilst the campaign has been launched with the slogan ‘Get Ready’, it has been reported that ‘Take Back Control’ was previously under consideration by the government, before being dismissed as too overtly partisan, it being the slogan of the official Leave campaign.
“I think, from the outset, this campaign has been shaped by party-political considerations.”
HuffPost UK has contacted Downing Street for comment.
The accusation tops a damaging week for Johnson’s authority after the Court of Session ruled his controversial decision to shutdown parliament ahead of Brexit was unlawful.
The PM, who has lost his majority in the Commons after throwing 21 of his own MPs out of the party for voting against him, also faced six successive defeats in the Commons over the anti-no-deal Brexit bill.
Johnson strongly denied claims he misled the Queen over the prorogation of parliament when he sought the monarch’s consent for the five-week shutdown.
He insists the move allows the government to bring forward a new domestic agenda.