No real progress can be made in reaching a Brexit deal until the UK submits formal written proposals, Jean-Claude Juncker has said.

The European Commission president said there remains a “palpable” risk of a no-deal Brexit despite “friendly, constructive and in part positive” talks with Boris Johnson earlier this week.

The main stumbling block is the Prime Minister’s insistence on scrapping the backstop, the contingency plan aimed at preventing a hard border with Ireland by keeping the UK closely aligned to Brussels’ rules.

Mr Juncker told MEPs in Strasbourg: “I said to Prime Minister Johnson that I have no emotional attachment to the safety net, to the backstop, but I stated that I stand by the objectives that it is designed to achieve.

“That is why I called on the Prime Minister to come forward with operational proposals, in writing, for practical steps which would allow us to achieve those objectives.

“Until such time as those proposals have been presented I will not be able to tell you, looking you straight in the eye, that any real progress has been achieved.”

With the Brexit deadline set for October 31 and Mr Johnson insisting he will not seek an extension despite a law aimed at forcing him to do so if there is not a deal in place, Mr Juncker said the commission is prepared to work “day in, day out, morning until night” on efforts to reach an agreement.

“But I am not sure that we will get there,” he said.

EU chief negotiator Michel Barnier said the bloc still needs to hear more from the UK side about its proposals for replacing the backstop.

Michel Barnier
The EU’s chief Brexit negotiator Michel Barnier also addressed MEPs (Jean-Francois Badias/AP)

“The new UK Government this week in Luxembourg outlined the aspects of the backstop they don’t like. That is not enough, however, to move towards achieving a solution,” he said.

Winding up the debate in the European Parliament, he said the negotiations had reached a “critical juncture”.

“Three years after the referendum, we are at a moment of truth in these negotiations. It is a moment where we need to keep a clear head, we need to remain respectful of one another,” he said.

The Government is yet to hand over formal submissions and while written proposals have been produced, they have been taken back at the end of meetings to prevent them being leaked by the EU or member states.

Finnish European affairs minister Tytti Tuppurainen told MEPs it is a “rather bleak situation”.

Ms Tuppurainen, whose country holds the rotating presidency of the council of the EU, said: “In July the UK got a new Government and a new Prime Minister. Unfortunately it is increasingly clear that it has not helped to clarify the situation or the UK’s negotiating position.

“When it comes to the most difficult questions – such as the Irish border – the UK has not tabled any new concrete proposals yet.”

Jean-Claude Juncker
The EU side is ready to negotiate day and night, Jean-Claude Juncker, left, said (Jean-Francois Badias/AP)

She added: “The latest developments in Westminster and the call for a further extension make it very difficult to predict how things will unfold.

“We have to acknowledge that, currently, a no-deal on October 31 is a quite likely outcome.”

The debate in Strasbourg came as Jeremy Corbyn set out his approach to Brexit, with a hint that he would remain neutral in any referendum called by a Labour government.

Writing in The Guardian, Mr Corbyn said: “A Labour government would secure a sensible deal based on the terms we have long advocated, including a new customs union with the EU; a close single market relationship; and guarantees of workers’ rights and environmental protections.

“We would then put that to a public vote against Remain, and I pledge to carry out whatever the people decide, as a Labour prime minister.

“We are the only UK-wide party ready to put our trust in the people of Britain to make the decision.”