Jo Johnson has hinted that other ministers might consider quitting in protest of Theresa May's Brexit plan - one day after he resigned. Theresa May has said the withdrawal deal is 95% done - but there is no agreement yet on how to guarantee no hard border in Northern Ireland.
The resignation of such a high-profile figure, just days after Britain suggested it was close to a deal is seen as hugely significant. potentially leading to other Conservative MPs and Ministers speaking out in favour of a second referendum.
"To present the nation with a choice between two deeply unattractive outcomes, vassalage and chaos, is a failure of British statecraft on a scale unseen since the Suez crisis", he wrote, adding that from the work of his own Department he was aware that a no-deal scenario could threaten the country's access to fresh food and medicine.
"Given that the reality of Brexit has turned out to be so far from what was once promised, the democratic thing to do is to give the public the final say", he added.
Unless the government and the European Union intentionally change course, Brexit will happen by force of law on March 29 next year, with or without a deal.
Support for May's Brexit plan is dwindling, with the DUP today said to be furious over so-called "backstop to the backstop" proposals on the Irish border, which could divide the province from the rest of the United Kingdom on customs.
"My loyalty to my party is undimmed", Johnson added.
Asked if his brother Boris Johnson had lied to voters during the referendum about Brexit, the former transport minister said: "In the campaign there were undoubtedly promises made that have shown to be undeliverable. But my duty to my constituents and our great nation has forced me to act".
"The prime minister thanks Jo Johnson for his work in government". Meanwhile, a spokesman for May's office says there will not be a second referendum on Brexit under any circumstances.
Mr Johnson is the sixth minister in Theresa May's government to resign specifically over Brexit, following David Davis, Boris Johnson, Philip Lee, Steve Baker and Guto Bebb.
If a deal is voted down by parliament, the country could be thrust into an uncertain future: leaving abruptly without a deal, the collapse of May's government, an election, or, as some opponents of Brexit hope, a new referendum.
Former BBC journalist and current University of Kent chancellor Gavin Esler said: "This - from a hugely respected minister - is an important development".