Theresa May’s chief of staff has triggered a civil war in Downing Street by telling Cabinet Ministers that a second EU referendum is the only way to break the Brexit deadlock.

Gavin Barwell, the Prime Minister’s most powerful and influential adviser, is understood to have decided that plans should be drawn up for another public poll. But his incendiary suggestion has been greeted with fury from Brexiteers in the Cabinet.

Meanwhile, The Mail on Sunday can reveal that Mrs May’s deputy, David Lidington has held a series of secret meetings with Labour MPs to build a ‘coalition of the willing’ to force a new EU vote.

Theresa May (pictured today in Maidenhead with husband Philip) has repeatedly insisted there cannot be another referendum on Brexit

Gavin Barwell (left), the Prime Minister’s most powerful and influential adviser, is understood to have decided that plans should be drawn up for another public poll. Meanwhile, The Mail on Sunday can reveal that Mrs May’s deputy, David Lidington (right) has held a series of secret meetings with Labour MPs to build a ‘coalition of the willing’ to force a new EU vote

Yesterday, the Prime Minister tried to distract attention from the splits in her Government by launching a blistering attack on Tony Blair, accusing him of undermining her negotiations by encouraging Brussels to think that the UK will opt for a second referendum if her deal falls. Mrs May said: ‘There are too many people who want to subvert the process for their own political interests rather than acting in the national interest. For Tony Blair to go to Brussels and seek to undermine our negotiations by advocating for a second referendum is an insult to the office he once held and the people he once served.

‘We cannot, as he would, abdicate responsibility for this decision. Parliament has a democratic duty to deliver what the British people voted for. I remain determined to see that happen. I will not let the British people down.’

No 10 is primed this weekend for an attempt by Labour leader Jeremy Corbyn to try to capitalise on Mrs May’s problems by calling a vote of no confidence in the Government before Christmas. If a majority of the 650 MPs of all parties in the Commons backed the motion, it could lead to a General Election.

Aides’ nerves were not calmed by a poll released last night giving Labour a three-point lead. The Populus poll put Labour on 40 per cent, the Conservatives on 37 per cent and the Liberal Democrats on seven per cent. The pivot towards a possible second referendum will enrage the pro-Brexit backbenchers who led last week’s failed attempt to topple Mrs May.

Mrs May had to endure a vote of no confidence in her leadership of the Tory party on Wednesday. She nwon by 200 votes to 117

The Prime Minister was forced to pull the meaningful Commons vote on her Brexit deal after party whips told her she was likely to lose by a large margin, prompting backbenchers, led by Jacob Rees-Mogg’s hard-Brexit European Research Group (ERG), to force a vote of no confidence in her leadership of the Tory party. Mrs May won by 200 votes to 117.

The Prime Minister subsequently failed to persuade the EU to offer a compromise on the notorious Northern Ireland ‘backstop’, leaving aides to conclude that she is unlikely to win the Commons round to her deal. That leaves just three realistic options: a softer Norway-style Brexit, a No Deal exit or a second referendum.

With large sections of the Tory party adamantly opposed to Norway, and a majority of MPs set against No Deal, The Mail on Sunday understands that Mr Barwell is considering the second public poll.

Sources say that Mr Barwell has told the pro-Remain ‘gang of five’ Cabinet Ministers – Mr Lidington, Chancellor Philip Hammond, Work and Pensions Secretary Amber Rudd, Justice Secretary David Gauke and Business Secretary Greg Clarke –that a second vote is ‘the only way out of this’.

But the idea is being fiercely opposed by pro-Brexit Cabinet ministers led by Home Secretary Sajid Javid, Commons leader Andrea Leadsom and International Development Secretary Penny Mordaunt, who argue that it would be greeted with fury – and possibly civil disorder – by people who had voted for Brexit two years ago. And it puts Mr Barwell at loggerheads with the Prime Minister, who told this newspaper last week that the 2016 referendum was the only ‘people’s vote’ required.

The husband of Britain's Prime Minister Theresa May, Philip, stands with Number 10 Chief of Staff Gavin Barwell, as Mrs May speaks outside 10 Downing Street after a confidence vote by Conservative Party Members of Parliament on Wednesday

However, Mrs May’s political capital has been damaged by the size of the vote against her on Wednesday. One senior source said: ‘The PM is just a hostage of the Cabinet and her feuding aides’.

Ms Rudd hinted heavily about her support for a second referendum yesterday when she said that MPs across the parties should try to ‘forge a consensus’ over Brexit.

She said: ‘We need to find a plan that a majority in Parliament can support. We need to try something different. Something that people do in the real world all the time, but which seems so alien in our political culture – to engage with others and be willing to forge a consensus’.

Could we even agree the question? Before a second referendum could take place, there would be a bitter row over how it would work. Some in No 10 see a chance to bypass Parliament and get public support for Theresa May’s deal by pitching it in a straight fight with No Deal. But Remainers say there must be an option to stay in the EU on the ballot paper – a scenario we have imagined above – and would use the Commons to try force it. Three options: How a second referendum paper might look However a three-way question would not produce a conclusive result and would probably fall foul of electoral law. Therefore there could even be multiple rounds of voting, like a French presidential, election that would see No Deal go head-to-head with Remain in round two, if Mrs May’s deal was rejected in a first vote. Ministers are divided over whether Brexit could be delayed or stopped without new legislation. Attorney General Geoffrey Cox told Cabinet a new Act would have to be passed, but secret Government legal advice says Mrs May could unilaterally halt our exit using Royal Prerogative. How the 2016 ballot looked for the EU referendum Advertisement

Cabinet Office Minister Mr Lidington has led the secret efforts to drum up support for a second poll by meeting senior Labour figures such as former Europe Minister Chris Bryant. Other ‘back channels’ have been established between Tory former Education Secretary Nicky Morgan and Labour’s Yvette Cooper and between Tory Anna Soubry and Labour leadership hopeful Chuka Ummuna.

But the discussions have revealed bitter differences over the wording of any referendum question, with No 10 indicating that it should be between Mrs May’s deal or No Deal. Labour MPs have made clear that the price of their support would be including Remain as an option.

Downing Street has been warned that some members of the ERG would be prepared to vote with Jeremy Corbyn in a Commons confidence motion, or abstain, rather than allow a second referendum.

Last night, former Tory leader Iain Duncan Smith described Mr Lidington’s manoeuvring as ‘utter madness’.

He told The Mail on Sunday: ‘I don’t believe he has ever accepted we will leave. Doing deals with a Labour Party run by Jeremy Corbyn is literally madness, utter madness. All the polling says if there is a second referendum we will plunge at the next Election. We will not be re-elected if we do not deliver Brexit.’

Mr Duncan Smith said Mr Lidington’s actions encouraged the EU to play hardball in negotiations in the expectation that MPs would call a second referendum rather than risk No Deal.

‘They are making it very hard for the PM to negotiate,’ he said. ‘The EU just don’t believe we are willing to walk away.’

Meanwhile, Brexit supporting Cabinet Ministers such as Ms Leadsom and Ms Mordaunt are pushing for a ‘managed No Deal’ option. It would involve the UK paying up to £20 billion for a ‘standstill’ two years in which Britain would mirror all EU rules to allow both sides to prepare for a hard exit.

Mrs May’s allies accuse Mr Rees-Mogg’s ERG of making a second referendum more likely by sabotaging the Withdrawal Agreement.

One Brexiteer Minister described the anger in Government over the abortive coup: ‘They like to present them as Jesuitical true believers, but they are more like jihadists’.

The Populus poll, carried out for Best for Britain, a pro referendum group, found that while 74 per cent of Labour voters support a second referendum, a majority of Tory voters, 51 per cent, are against.