Labour has a duty to prevent a no-deal Brexit, Sir Keir Starmer has said as the party appeared set to back the option of a fresh referendum on European Union membership.

Delegates at the party’s conference in Liverpool are expected to back a plan that could lead to a fresh public vote which could include the option of ditching Brexit altogether.

Sir Keir, who said he would vote to stay in the EU if that was an option, played down the divisions at the top of the party over the plan.

Under the terms of the motion set to be voted on at the conference on Tuesday, if Labour cannot force an early general election it will “support all options remaining on the table, including campaigning for a public vote”.

Shadow Brexit secretary Sir Keir said the scope of the motion was “wide enough to encompass the option of Remain” in any referendum.

His comments came after shadow chancellor John McDonnell signalled he would want any second Brexit referendum to be limited to choosing how to leave the EU.

But Sir Keir told the BBC: “There isn’t this difference of opinion between me and John McDonnell and the whole Labour Party is united around the motion that is going forward this morning.”

Labour appears set to reject Theresa May’s Brexit plan, claiming it fails to meet the party’s tests for any deal.

“Looking at the state of the negotiations, which are frankly chaotic and failing, it looks like she is not going to meet those tests so in those circumstances we will vote against a deal that she brings back,” he added.

Sir Keir said if Mrs May’s plan was rejected by Parliament she should call an election but if that does not happen then Labour would keep all options open.

The possibility of another referendum after 17.4 million voted to leave the EU has led to fears of civil unrest and the rise of far-right politics.

But Sir Keir said that could be avoided and the party had a responsibility to save the UK from leaving without a deal.

A no-deal Brexit would “rupture our trading arrangements and this will cost jobs, I don’t doubt that the pound will begin to drop”.

“We won’t have any arrangements for security and counter-terrorism – I worked, when I was director of public prosecutions, on counter-terrorism work across Europe – the idea that we wouldn’t have an arrangement in place for that would horrify people,” he told BBC Radio 5 Live.

“And frankly this idea that we might have medicines stockpiled for six weeks has spooked people.

“We don’t want to face that situation and we have got a duty to do something to stop it and that’s why the option of a public vote is important as something that may have to happen when we get to that stage.”

Acknowledging the sensitivity of the issue he said: “We have to manage it in a sensible way but we have to accept we are only having this discussion because of the failure of the talks.”

Activists marched in favour of a referendum at Labour's conference in Liverpool (Peter Byrne/PA)
Activists marched in favour of a referendum at Labour’s conference in Liverpool (Peter Byrne/PA)

Labour’s position leaves the Prime Minister brutally exposed to a rebellion by restive Tory backbenchers, with fewer than a dozen able to fracture her fragile control of the Commons in the upcoming vote.

Sir Keir confirmed talks were taking place with potential rebels, adding: “There is a consensus in the House of Commons that this is not what anybody expected to happen and there is a consensus that we cannot simply allow no deal to happen because of the failure of these negotiations.

“I think if we get to that stage this autumn, most MPs would be prepared to say ‘we need to do something to prevent us crashing out of the EU without a deal’.”

Sir Keir released an analysis of the Brexit blueprint agreed by the Cabinet at Mrs May’s country residence, which he said showed it failed to pass Labour’s six tests.

The tests demand a “strong and collaborative” future relationship with the EU; the “exact same benefits” as single market and customs union membership; fair management of migration; defence of rights and protections; protection for national security; and delivering for all regions and nations of the UK.

Brexit minister Robin Walker accused Labour of trying to take the UK “back to square one” and of wanting to re-run the referendum, saying: “Labour promised to respect the referendum result, but are just playing political games and trying to frustrate it.”