Theresa May is hoping to keep details of the UK’s EU divorce bill a secret until after the Conservative Party conference – to avoid a damaging revolt by Brexit supporters

Theresa May is hoping to keep details of the UK’s EU divorce bill a secret until after the Conservative Party conference – to avoid a damaging revolt by Brexit supporters.

The Mail on Sunday understands that the Prime Minister has been advised that Britain is likely to have to fork out up to €50 billion – £46 billion at current exchange rates – as the only way to break the deadlock of the Brexit talks.

But anticipating a backlash from her party’s anti-EU wing, Mrs May hopes to wait for the Tories’ Manchester conference to conclude on October 4 before announcing the details.

That would give her just two weeks before a critical summit takes place at which the EU will determine whether enough progress has been made on agreeing the divorce bill to allow trade talks to start.

It came as Mrs May last night urged rebels in her party not to obstruct the EU Withdrawal Bill – which will pave the way for our exit – when it starts it progress through the Commons this week. She described it as ‘the single most important step we can take to prevent a cliff-edge for people and businesses.’

Mrs May added: ‘We’ve had frank negotiations with the Commission, and we’ve travelled the globe to establish the trading relationships of the future. Now it is time for Parliament to play its part’.

Mrs May is desperate for the Manchester conference to act as a springboard for her to reassert her authority over a party still bruised by June’s General Election disaster.

She hopes to ‘sell’ the deal to her restive backbenchers – some of whom think we should not pay any divorce money to Brussels – by arguing that agreeing to the higher figure would ‘only’ mean writing an annual cheque for £15 billion or so over a three-year transition period following our departure in March 2019.

She would highlight that this is just £7 billion more per year than our current net contribution to the EU.

Although the UK is expected to make an opening offer of about €36 billion (£33 billion), Government advisers believe this figure will have to go a lot higher by the time the summit starts on October 18.

It came as Mrs May (pictured in Tokyo on Friday) urged rebels in her party not to obstruct the EU Withdrawal Bill when it starts it progress through the Commons this week

The European Commission’s chief Brexit negotiator, Michel Barnier, is refusing to accede to Brexit Secretary David Davis’s demand for trade discussions to start until agreement is reached on the price we should pay for severing our ties.

Mr Davis believes any transitional period, during which the UK would continue to enjoy many of the benefits of the single market and customs union, should be limited to a maximum of two years, but a three-year spell – favoured by Chancellor Philip Hammond – would allow the lump sum to be split into smaller annual payments.

Prior to June’s botched Election, No 10 was expecting to have to hand over only about £30 billion. Mrs May’s critics will argue that her lost parliamentary mandate has cost the country by reducing her leverage with EU negotiators.

Asked about Mrs May’s bid to keep the EU divorce bill a secret, a Downing Street spokesman said: ‘We don’t recognise this version of events.’