Labour deputy leader Tom Watson said the party has a duty to talk to Theresa May if she is prepared to enter into an “intelligent conversation” on Brexit.

Following the crushing defeat of the Prime Minister’s Brexit deal, Mr Watson said there could be no “blank cheque” and they would have to establish that she is prepared to talk seriously.

Speaking at the Fabian Society’s new year conference in London, he said that in the current climate of uncertainty Jeremy Corbyn was entitled to insist there was an element of trust for any discussions to take place.

Mr Corbyn is the only Westminster party leader to have refused to meet the Prime Minister following the overwhelming rejection of her withdrawal plan, insisting she must first rule out a no-deal Brexit.

Fabian Society new year conferenceLabour deputy leader Tom Watson addressed the Fabian Society new year conference at Friends House in London (Stefan Rousseau/PA)

Speaking during a question and answer session, Mr Watson said the party had a duty to respect the result of the 2016 EU referendum.

“We are obligated, I think, through our sense of patriotism and respect for democracy to have an intelligent conversation on Brexit with Theresa May if she is offering it. But there is no bargain basement Brexit on our agenda,” he said.

Mr Watson said there was “some turbulence” around the talks which took place in Westminster, and that Labour needed to establish whether Mrs May was serious in seeking to build a consensus on the way forward.

“In the current uncertainty it is not unreasonable for Jeremy Corbyn to say to Theresa May ‘If you are looking for a broader consensus after two years of blocking out all other political leaders and half her own Cabinet, there needs to be a little bit of trust,'” he said.

“There is some turbulence at the moment that needs ironing out. We need to work out how serious she is, what concessions she is serious about, is she actually serious about negotiations or is she just trying to pressure her own MPs?”

Earlier, shadow Brexit secretary Sir Keir Starmer drew loud cheers when he said the option of campaigning for a second referendum, if the party is unable to force a general election, must remain on the table.

“That is a very important commitment. It’s a commitment to you, our members and our movement. And it is one we will keep,” he said.

“A public vote has to be an option for Labour. After all, deeply embedded in our values are internationalism, collaboration and cooperation with our European partners.”

Following a tumultuous week, Mrs May was spending the weekend at her official country retreat at Chequers contemplating her next move ahead of a statement to MPs on Monday.

Meanwhile, it was reported former attorney general Dominic Grieve is preparing an amendment which would enable MPs to seize control of the Commons business to block a no-deal Brexit.

According to a text seen by the BuzzFeed News website, the amendment, if approved, would allow a motion put down by 300 MPs – less than half the House of Commons – to stand as first business of the day.

They would have to include MPs from across five parties – including 10 from the governing party.

That could allow a cross-party coalition of MPs to take control of the business of the House from the Government – in contravention of normal constitutional conventions – and table a bill blocking no-Brexit which would almost certainly be passed.

Mrs May has strongly resisted calls to rule out no-deal, warning it would remove her leverage in negotiations in Brussels,

There was no immediate comment from Mr Grieve.

Earlier, Sir John Major called for a free vote for MPs in a series of “indicative votes” on the various alternative Brexit plans which had been put forward to break the deadlock in Parliament.

As an “act of statesmanship”, he said all the party leaders should give their MPs a free vote to allow an “honest representation” of opinion in the House.

“It is the only way to get an absolutely honest answer from Members of Parliament and if it is a free vote it removes the danger of resignations from Government or the opposition frontbench because they disagree with their leader’s policy,” he told the BBC Radio 4 Today programme.

“It is a unique way of doing it but I think it is justified.”