Sky News' political editor Faisal Islam said: "It is awful news for the Government that Jo Johnson - who was helping to organise no deal planning for the trade border - resigns in this way with an extra vote against the withdrawal agreement".
Mrs May is said to have told Brexiteers the plan was "not needed yet" but it received a "surprisingly warm" response from Chancellor Philip Hammond, a senior source told Sky News. Supporting a bad deal is not in the national interest.
"My brother Boris, who led the leave campaign, is as unhappy with the Government's proposals as I am".
"The gap between what was promised during the campaign before the referendum, and that now offers the Prime Minister in his project deals is so wide that I had no choice but to pass this afternoon to the Prime Minister's statement about his resignation", said Johnson.
A spokesperson for May's office said later Friday that under no circumstances would a second referendum be held. Now his lesser-known brother Jo, who was also a government minister, has followed him out.
The Labour leadership says it is highly unlikely it will vote for the government's current plan.
Writing in Saturday's Daily Telegraph, she said she had raised DUP concerns with Mrs May, but the PM's response failed to allay their fears. "We are now faced with the reality of that in the form of the deal that the prime minister is about to bring back before parliament".
"The "new" idea of a United Kingdom customs arrangement does not appear to be a genuinely UK-wide offer but a GB offer and an NI offer badged as one - Northern Ireland in THE EU customs territory and GB in A customs union".
DUP officials said Northern Ireland is an inalienable part of the United Kingdom and said they would not tolerate any attempts at putting a border between Belfast and the rest of United Kingdom as a way to keeping an open border between Northern Ireland and Ireland.
Kristian Rouz - A new report claims at least four members of Britain's Conservative and Unionist cabinet of Prime Minister Theresa May could resign from their positions due to their dissatisfaction with May's handling of the Brexit process.
Ms Thornberry said Mr Corbyn's comments had to be seen in context and he was explaining that: "We had a referendum, that we are democrats over and above everything else".
"This is, without doubt, the single most important decision we are going to make in our modern history".
"It was meant to be about a fearless new future as a deregulated economy".
She was asked about party leader Jeremy Corbyn's comment to a German newspaper that Brexit can not be stopped.
Asked by German magazine Der Spiegel if he would stop Brexit if he could, the Labour leader said: "We can't stop it".