MPs will today vote on a series of Commons amendments hoping to wreck her plan for a “common rule book” covering a new “UK-EU free trade area”.
Even if the measures do not pass, the rebels hope the show of strength will be enough to pressure the Prime Minister into retreat.
The Tory divide over Brexit deepened last night after ex-minister and arch-Remainer Justine Greening called for a second referendum.
She claimed Theresa May’s controversial Brexit plan, agreed at Chequers by her Cabinet earlier this month, was the “worst of both worlds”.
She said: “Having read the detail, this deal is a fudge I can’t support. It’s the worst of both worlds.
“The only solution is to take the final Brexit decision out of the hands of deadlocked politicians, away from the backroom deals, and give it back to the people.”
Ms Greening, who represents the London seat of Putney, is the most high-profile MP to back a second referendum.
The Prime Minister was dealt a further blow as MP Scott Mann resigned as a parliamentary aide in protest at the Prime Minister’s Brexit stance.
Follow today’s latest Brexit news with the Express.co.uk live blog below…
Theresa May faces a Commons showdown with Brexiteer Tory MPs
1:51pm: Defence Secretary Gavin Williamson has said he is opposed to a second Brexit referendum.
Asked at Farnborough International Airshow if another vote should be on the Government’s agenda, he replied: “Not at all.
“The British people had a referendum. They had their say and we need to deliver on it. That’s what we’re doing.”
1:38pm: Former Attorney General Dominic Grieve has accused Brexiteers of trying to cause “chaos” for the Government.
The pro-EU Tory said he wanted to “help get this country through a Brexit process that is endangering its stability and its wellbeing”.
He added “As matters stand, trying to get rid of the Prime Minister or fatally undermine her – I fail to see how that’s going to take matters forward.”
Theresa May speaks to guests at the Farnborough Airshow this morning
12:39pm: Negotiations on the withdrawal agreement and future relationship have resumed at official level in Brussels today.
New Brexit Secretary Dominic Raab is due to hold his first face-to-face talks with the EU’s chief negotiator Michel Barnier tomorrow.
Labour criticised Mr Raab for failing to attend the start of the new round of talks, saying his absence was “simply not good enough”.
The party’s Brexit spokeswoman Jenny Chapman said: “Over the past week the Government’s Brexit strategy has descended into utter chaos.
“But rather than trying to repair the damage and negotiate with Brussels, the new Brexit Secretary has decided to take the evening off and attend a summer drinks reception.”
12:17pm: The Prime Minister’s spokesman has ruled out the possibility of the Government holding a second Brexit referendum.
Dismissing calls from ex-Cabinet minister Justine Greening, the spokesman said: “The British public have voted to leave the European Union.
“There is not going to be a second referendum under any circumstances.
“The Prime Minister is very clear that the proposal we put forward at Chequers delivers on the will of the people in the referendum.”
Theresa May said Brexit will be a massive boost for Britain’s aerospace industry
11:21am: Prime Minister Theresa May has said Brexit will be a massive boost for Britain’s aerospace industry.
During a visit to the Farnborough Airshow, Mrs May spoke to aviation industry executives and UK business leaders about her Brexit plans.
She said: In her speech, the Prime Minister is expected to say: “We can all feel incredibly proud of our position as a leading aerospace nation.
“By working closely together, Government and industry have ensured we remain at the forefront of civil aviation and that our air power is second to none.
“I want us to build on that, and ensure that in an increasingly competitive industry we make the most of the opportunities that lie ahead.”
10:35am: Tory MP Scott Mann has resigned as a parliamentary aide in protest at Theresa May’s Brexit stance.
In a letter to the Prime Minister, the North Cornwall MP said he could not let his constituents down by backing the Government’s “watered-down Brexit”.
He added: “The residents of North Cornwall made it very clear that they wish to have control over fishery, our agriculture policy, our money, our laws and our borders.
“I will evaluate those core principles against the Brexit white paper and ensure that I vote in line with their wishes.”
Net migration from the EU has fallen to its lowest level in nearly five years
10:25am: Net migration from the EU has fallen to its lowest level in nearly five years, official figures show.
An estimated 101,000 more people arrived in the UK from the bloc than left in 2017, according to the first data for a full calendar year since the vote.
The latest figure is the lowest for any 12-month period since the year to March 2013, when it stood at 95,000.
Overall net long-term migration, which includes arrivals and departures of non-EU nationals, was around 282,000 in 2017.
9:22am: Business Secretary Greg Clark has warned Tory would-be rebels against supporting amendments tabled by arch-Brexiteers.
He claimed the amendments risked harming the country’s ability to trade after leaving the European Union.
He told the BBC: “The amendments are to a Bill that is designed to prepare for the world after Brexit, to be able to establish new customs regime that will be necessary.
“So I would hope and expect that those of my colleagues that want to get on with Brexit would recognise that this Bill is essential.”