Boris Johnson has vowed Tory MPs will not let Theresa May 'surrender' to a soft Brexit, despite her moves to potentially broker a deal with Labour leader Jeremy Corbyn.

The Tory leadership hopeful claims an agreement with Corbyn on remaining in a customs union 'would make a total and utter nonsense of the referendum result'.

He said: 'To agree to be non-voting members of the EU, under the surrender proposed by Jeremy Corbyn - it cannot, must not and will not happen.'

Mrs May paved the way for a customs union deal with Labour last night as she pledged to 'compromise' to ensure Brexit happens.

In an informal statement aimed directly at voters, Mrs May argued she had no choice but to try to find a cross-party agreement with Jeremy Corbyn because otherwise Britain might not leave the EU at all.

She said the referendum campaign was not fought on party lines and the public wanted to see politicians 'working together more often'.

But Mrs May's approach is flatly contradicted by Mr Johnson today.

Writing in The Daily Telegraph, he slams the Prime Minister for meeting 'a man who still believes in the precepts of Bolivarian revolutionary socialism, even though they have reduced Venezuela to destitution'.

He adds: 'If we Tories have one duty, it is to prevent this man getting anywhere near the levers of power.

'So it seems utterly incredible that he has now been invited into Downing Street to negotiate a Brexit deal.

'And it is doubly incredible that the government is – so we are told - willing to accede to his terms.'

Mr Johnson claims the Tories would be 'tearing up a promise made thousands of times in parliament and elsewhere' by acceding to Corbyn's demands.

Writing in The Daily Telegraph, he said: 'If the UK were to commit to remaining in the Customs Union, it would make a total and utter nonsense of the referendum result.

'We would be out of the EU, but in many ways still run by the EU.

'It would be the worst of both worlds, not just now, but forever – and that is why I find the news so appalling that I don't really believe it.'

Formal talks between No 10 and Labour broke down on Friday night, but are expected to begin again today after informal contact over the weekend.

In an attempt to break the deadlock, Mrs May could agree to accept elements of Labour's plan for a 'softer' Brexit, including a customs union and alignment with EU rules on employment and the environment. No 10 is also considering whether to make elements of the deal legally binding to prevent them being torn up by Mrs May's successor.

Dubbed a 'Boris-lock' (after Mr Johnson), this would mean putting into law some elements of the agreement so a parliamentary vote would be needed to overturn them.