"I think it is imperative that we now go back to the people and check that they are content to proceed on this extraordinary basis", he explained.
Calling for a second referendum to be held on Brexit, Mr Johnson denounced the choice between her deal or no-deal as a "failure of British statecraft on a scale unseen since the Suez crisis" that had left Britain facing "vassalage" or "chaos".
The UK needs to "pause and reflect" before doing something "irrevocably stupid" over Brexit, Jo Johnson said a day after quitting as a minister.
Brexit negotiations have put Britain on the brink of the greatest crisis it has faced since the Second World War, Transport Minister Jo Johnson warned in his resignation letter.
Tory MP Anna Soubry, a vociferous Remain campaigner, said she had "huge respect" for Mr Johnson, telling The Guardian: "Jo isn't the only minister who shares these views and I hope others will follow his lead".
'On this most crucial of questions, I believe it is entirely right to go back to the people and ask them to confirm their decision to leave the European Union and, if they choose to do that, to give them the final say on whether we leave with the prime minister's deal or without it, ' he said. That's why I voted to start the Article 50 process and for two years have backed the prime minister in her efforts to secure the best deal for the country.
He added: "In the sense that if you betray the British people where they no longer believe in democracy... you don't know what the consequences are".
When we get the final deal, and it feels like that's not very far away, Cabinet ministers will have to look into their hearts and see whether or not they feel they can support it.
Downing Street thanked him for his work but continued to insist there was no prospect of another referendum "under any circumstances".
Labour said the resignation - the 18th during the PM's tenure - showed May had lost authority and could not negotiate Brexit.
"Theresa May is in office, but not in power".
Jo Johnson's resignation, and his call for a fresh referendum to test voter sentiment, further complicates matters for May as she tries to strike a deal with European Union leaders that would pass muster with her own cabinet and win backing in Parliament. He has resigned on an issue of principle putting the country before his party and his own career.