The Prime Minister in Downing Street today ahead of the Cabinet sub-committee meet

Downing Street tonight insisted 'nothing is agreed until everything is agreed' after a secretive summit of senior ministers to discuss signing off on a £40billion Brexit divorce bill.

Theresa May was today warned that 'one pound is too much' to give Brussels as she gathered her Brexit 'war Cabinet' to discuss hiking Britain's offer.

A meeting of 10 of Mrs May's most senior ministers gathered for what could prove to be one of the crucial moments in the Brexit process.

But as the meeting broke up after more than two hours, No 10 sources said the UK and EU must 'step forward together'.

Ahead of the Downing Street summit, the Prime Minister faced a cacophony of complaints from Tory backbenchers who said the public would 'go bananas' if the government doubles its offer to the EU.

Senior Brexiteers Boris Johnson and Michael Gove are believed to be ready to agree to the increase - but are demanding concrete assurances from Brussels about trade talks.

Before her ministers gathered, Mrs May refused to be drawn on the details of the proposal that will be discussed.

Chancellor Philip Hammond said yesterday that Britain was preparing to table a new compromise deal ahead of an EU summit next month when leaders are due to decide whether to begin post-Brexit trade talks with the UK.

Mr Hammond declined to give a figure, but Brussels sources have suggested the EU will not consider a payment of less than £40billion - double the figure previously floated by Mrs May.

Foreign Secretary Boris Johnson left No 10 late tonight following a marathon summit of top ministers to decide whether to offer the EU more money for Brexit

Mr Johnson is thought likely to support a higher offer to trigger trade talks amid a major Cabinet row over how much to concede

In September, the Prime Minister offered to hand over £20billion during a two-year transition to a new relationship after Brexit in 2019.

But EU leaders rejected the offer as too small. Some hardliners in the European parliament are demanding up to 100billion euros.

Ministers on a key Cabinet sub-committee are due to hold talks behind closed doors this afternoon on how much to offer the EU, and what to demand in return.

Mr Johnson and Brexit Secretary David Davis have both warned the Prime Minister against making a significant new offer unless it is accompanied by guarantees on the type of trade deal the UK can expect from Brussels.

But the Chancellor yesterday indicated he was backing a bigger payment, saying there was a 'very high value' in having a close trade relationship with the EU after Brexit.

David Davis and Michael Gove, pictured in Downing Street this evening, are also due to be attending the Cabinet sub-committee session

Foreign Secretary Boris Johnson was in Downing Street this morning ahead of the crunch talks this evening

Talking up the prospect of a new offer, he told the BBC's Andrew Marr Show: 'I do think we're at something of a turning point. We've had a difficult year.

'We're now I think on the brink of making some serious movement forward in our negotiations with the European Union, and starting to unlock that logjam so that people can start to see clarity about the future.'

Any figure in the order being demanded by the EU would leave Mrs May at risk of a huge backlash from Tory MPs - who have made clear they do not believe Britain has any legal obligations to pay.

Senior MP Nigel Evans told MailOnline Britain had already made the running in the negotiations and put a good offer down on money.

WHO IS IN THE PM'S BREXIT 'WAR CABINET' There are 10 ministers in the sub-committee that will discuss the divorce bill offer today: Prime Minister Theresa May First Secretary of State Damian Green Chancellor Philip Hammond Home Secretary Amber Rudd Foreign Secretary Boris Johnson Brexit Secretary David Davis Trade Secretary Liam Fox Business Secretary Greg Clark Environment Secretary Michael Gove Defence Secretary Gavin Williamson Advertisement

He said: ‘We are the ones who have talked about transition, we offered £20billion extra funding.

‘That has to be in their interests to stop a black hole that Germany and France would have to fill.

‘That is British taxpayers money for public services, not for Brussels bureaucrats.’

Former minister Robert Halfon said voters would not understand if the Tories handed over huge sums to Brussels after years of austerity.

'If we start saying that we're going to give £40billion to £50 billion to the EU, I think the public will go bananas, absolutely spare,' he told BBC Radio 4's Westminster Hour.

'I cannot believe the public would accept such a huge amount when we need money for our schools, our hospitals, our housing, and many other things. I think that is going to be very difficult if it is going to be that amount of money.'

Fellow backbencher Jacob Rees-Mogg urged ministers to reject any further financial demands.

'It's a matter of choice for the Government – they will have to choose whether to give lots of money to the EU or spend money on necessary UK public services,' he said.

'I'd encourage the Government to choose our own domestic services, instead of expensive schemes in Europe.'

Trade Secretary Liam Fox (left) and Home Office Amber Rudd (right) were both in Downing Street this morning, and will attend the sub-committee meeting later

Another Tory MP Peter Bone said 'one pound is too much'.

'There is no legal obligation whatsoever for us to pay any money. We are net contributors, over £200billion over the years to to the European Union superstate.

'If anyone should get any money from this divorce, it’s us. The idea we would pay £38billion is absurd.

'I was at a meeting yesterday with constituents and they said, ‘Look, Peter, if you’ve got £38billion available, use it to support the NHS.’ I find that a pretty strong argument.'

Fellow Brexiteer MP Henry Smith said: 'Especially as Germany struggles to form a government, now is not the time for Britain to offer more money than her obligations are due in EU Brexit negotiations.

'The EU27 will of course miss UK cash but no deal would damage their economies and trade surplus with us far worse.'

Speaking on a visit to Birmingham ahead of the meeting this afternoon, Mrs May said: 'I set out in my Florence speech that we will honour our commitments. I was very clear about that, as I said - for the current budget plan - no other EU country needs fear that they will have to receive less or pay in more.

'We’ve been very clear that we will honour our commitments.'

Boris Johnson (pictured out jogging today) and Michael Gove (pictured right in Downing Street last week) are believed to be ready to sign off on an increased divorce bill offer, but are asking for guarantees from Brussels on trade

Chancellor Philip Hammond said during a BBC interview yesterday (pictured) that Britain was preparing to table a new compromise deal ahead of an EU summit next month

The Chancellor said the Government would make a fresh offer to Brussels ahead of an EU summit next month when leaders are due to decide whether to begin post-Brexit trade talks with the UK

The EU's chief negotiator, Michel Barnier, initially set a deadline of this Friday for a new offer, although this has now been extended for a further week.

France and Germany, which will have to plug the financial holes left by the UK's EU departure, have both indicated they will delay the opening of trade talks until they receive an improved offer.

German foreign minister Michael Roth said today that Britain must “move” on the financial settlement if it wants trade talks.

'It is about the money. In the end, it’s about the rights of the citizens of the EU and it’s about the money,' he said.

'I have already made it clear that the British must make a move. They must stand by their contractual obligations. They can’t be released from them.'

Ministers are desperate to begin talks on trade and a two-year transition deal at next month's EU summit in Brussels. Mr Hammond yesterday suggested ministers would act to ensure a deal, saying: 'We will make our proposals to the EU in time for the Council, I am sure about that.'

The Cabinet's Brexit strategy and negotiations sub-committee is due to meet today to try to thrash out an agreement on a new offer.

This could be put to a full meeting of the Cabinet tomorrow before being proposed to EU Council president Donald Tusk, who will travel to London for emergency talks with the Prime Minister on Friday.

Theresa May (pictured visiting an engineering training facility in Birmingham today) could face a rebellion over any big payment to the EU

Jacob Rees-Mogg (left) and Robert Halfon (right) are among the Tory MPs who have warned about handing over large sums as a divorce payment to the EU

But, despite Mr Hammond's assessment, there is no guarantee of agreement among ministers. One Cabinet source said there was an 'impasse' on the issue. Pro-Remain ministers have a narrow majority on the Brexit sub-committee.

But the Prime Minister is said to be reluctant to push ahead without the support of Brexiteers such as Mr Johnson, Mr Davis, Michael Gove and Liam Fox, who are all members of the committee. Mrs May will come under pressure today to get guarantees from Brussels on the future relationship with the EU before agreeing a new sum.

Failure to get agreement on the divorce terms next month will lead to renewed calls for the Government to prepare for leaving the EU without a trade deal.

And some pro-Remain MPs are also nervous about handing over large sums to Brussels without receiving guarantees in return.

Tory MP Stephen Hammond said he was not opposed to increasing the offer, but added: 'We have to be clear what we're paying for and what we're getting.'