EU leaders are set to issue an election result-day warning to Boris Johnson that he has only “limited” time to avoid a no-deal Brexit, leaked documents have revealed.

The prime minister has refused to rule out the possibility of crashing out without a free trade agreement (FTA) in December 2020, abruptly halting a press conference on Wednesday when he was challenged on the issue by The Independent.

Liberal Democrats said the developments exposed as a “fallacy” Mr Johnson’s claim to be able to “get Brexit done” on 31 January if he wins next week’s election, warning that the UK will instead be plunged into a race against time to avoid leaving on unfavourable World Trade Organisation terms at the end of next year.

In a draft communique set to be released by the remaining 27 EU member states on Friday next week – the day after the 12 December election – the European Council will warn of a new ticking clock with a fresh round of negotiations strongly resembling the past three years.

In a striking deja vu, the leak showed the leaders will confirm that Michel Barnier will reprise his role as chief negotiator, that there would be no side deals with individual member states, and that the issue will come to a head at a string of make-or-break EU summits.

Best pictures from Final Say Brexit march Show all 76 1 /76 Best pictures from Final Say Brexit march Best pictures from Final Say Brexit march Crowds march through central London Getty Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march Protesters gather in Parliament Square Led By Donkeys Best pictures from Final Say Brexit march Mayor of London Sadiq Khan joins protesters PA Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march Anti-Brexit protesters fill Parliament Square in London PA Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march A demonstrator marches EPA Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march People's Vote Final say march - 19 October 2019 Angela Christofilou Angela Christofilou/The Independent Best pictures from Final Say Brexit march Protesters push a float depicting Dominic Cummings using Boris Johnson as a puppet during the Final Say Brexit march in London PA Best pictures from Final Say Brexit march EU supporters react after the result of the vote on the deal delay was announced at the House of Commons REUTERS Best pictures from Final Say Brexit march A demonstrator carries his dog draped in EU flag AP Best pictures from Final Say Brexit march Thousands of people taking part in a People's Vote march AFP/Getty Best pictures from Final Say Brexit march Protesters use their flags to shelter from the rain Getty Images Best pictures from Final Say Brexit march Protesters march towards Parliament Square Getty Images Best pictures from Final Say Brexit march Anti-Brexit demonstrators carry placards and EU flags AP Best pictures from Final Say Brexit march Sir Oliver Letwin MP in Parliament Square, London, during an an anti-Brexit, Let Us Be Heard rally, after it was announced that the Letwin amendment, which seeks to avoid a no-deal Brexit on October 31, has been accepted PA Best pictures from Final Say Brexit march Thousands of people taking part in a People's Vote march UK BROADCASTERS POOL/AFP via Get Best pictures from Final Say Brexit march A protester with "Bollocks to Brexit" stickers on his head Getty Images Best pictures from Final Say Brexit march Demonstrators march EPA Best pictures from Final Say Brexit march Britain's main opposition Labour Party shadow Secretary of State for Exiting the EU Keir Starmer, shadow Home Secretary Dianne Abbott, shadow Chancellor of the Exchequer John McDonnell, shadow Foreign Secretary Emily Thornberry speaks on stage in Parliament Square AFP via Getty Images Best pictures from Final Say Brexit march Anti-Brexit supporters cheer outside parliament AP Best pictures from Final Say Brexit march A EU supporter waves flags REUTERS Best pictures from Final Say Brexit march Anti-Brexit supporters AP Best pictures from Final Say Brexit march Protesters shout and chant demanding a final say Getty Images Best pictures from Final Say Brexit march Police look towards protesters Getty Images Best pictures from Final Say Brexit march Pro-Brexit protesters outside the Houses of Parliament in London PA Best pictures from Final Say Brexit march People taking part in an Anti-Brexit, Let Us Be Heard march head to Parliament Square in London PA Best pictures from Final Say Brexit march People taking part in an Anti-Brexit, Let Us Be Heard march in Trafalgar Square PA Best pictures from Final Say Brexit march Anti-Brexit supporters cheer outside parliament AP Best pictures from Final Say Brexit march People taking part in an Anti-Brexit, Let Us Be Heard march past Trafalgar Square PA Best pictures from Final Say Brexit march Protesters shout and chant Getty Images Best pictures from Final Say Brexit march Cory (7) sits on his father's shoulders as protesters march towards Parliament Square Getty Best pictures from Final Say Brexit march People attend the 'Together for the Final Say' march EPA Best pictures from Final Say Brexit march Protesters march towards Parliament Square Getty Images Best pictures from Final Say Brexit march Mayor of London Sadiq Khan speaks on stage PA Best pictures from Final Say Brexit march A woman in EU costume EPA Best pictures from Final Say Brexit march Anti-Brexit protesters fill Parliament Square in London PA Best pictures from Final Say Brexit march Anti-Brexit protesters AP Best pictures from Final Say Brexit march Anti-Brexit protesters hold an Independent banner Angela Christofilou/The Independent Best pictures from Final Say Brexit march Protesters hold an anti-Brexit placard by The Independent stall during the Final Say Brexit march in London Tom Richell Best pictures from Final Say Brexit march Anti-Brexit protesters in Parliament Square, London, PA Best pictures from Final Say Brexit march Demonstrators hold placards and EU flags AFP/Getty Best pictures from Final Say Brexit march An anti-Brexit protester joins in the Final Say Brexit march on 19 October AP Best pictures from Final Say Brexit march EU supporters march in London REUTERS Best pictures from Final Say Brexit march Sir Patrick Stewart and Paul McGann join in the Final Say Brexit march in London on 19 October PA Best pictures from Final Say Brexit march EU supporters march Reuters Best pictures from Final Say Brexit march A demonstrator shouts into a megaphone as she marches AFP via Getty Images Best pictures from Final Say Brexit march A dog dressed in an anti-Brexit placard is walked in the Final Say Brexit march in London EPA Best pictures from Final Say Brexit march EU supporters march REUTERS Best pictures from Final Say Brexit march A morris dancer takes part in the Final Say Brexit march in London PA Best pictures from Final Say Brexit march Whippets are dressed in EU flag clothing during the Final Say Brexit march in London AP Best pictures from Final Say Brexit march Protesters march towards parliament in the Final Say Brexit march in London on 19 October 2019 PA Best pictures from Final Say Brexit march An anti-Brexit demonstrator takes part in the Final Say Brexit march in London AFP/Getty Best pictures from Final Say Brexit march EU supporters call on the government to give Britons a vote on the final Brexit deal Reuters Best pictures from Final Say Brexit march Anti-Brexit protesters Angela Christofilou/The Independent Best pictures from Final Say Brexit march An anti-Brexit protester Angela Christofilou/The Independent Best pictures from Final Say Brexit march Anti-Brexit protesters demonstrate in London during the Final Say Brexit march on 19 October AP Best pictures from Final Say Brexit march Protesters push a float depicting Dominic Cummings using Boris Johnson as a puppet during the Final Say Brexit march in London AFP/Getty Best pictures from Final Say Brexit march Protesters march towards parliament from Park Lane in the Final Say Brexit march in London on 19 October 2019 PA Best pictures from Final Say Brexit march Marchers visit The Independent stall during the Final Say March in London Tom Richell Best pictures from Final Say Brexit march An anti-Brexit protester holds a sign calling for a Final Say during a march in London EPA

The independent UK in a Changing Europe think tank warned this week that leaving without an FTA at the end of 2020 could deliver a hit of between 3.2 to 4.5 per cent to GDP, cutting the government’s annual income by up to £28bn.

The withdrawal agreement that Mr Johnson aims to implement next month involves the UK handing over a financial settlement of more than £30bn to Brussels and withdrawing from EU political structures, but does not guarantee the kind of trade deal that would avoid disruption to food and medicine imports and transport and the erection of tariff barriers.

The deal sets a tight deadline of just 11 months to complete an agreement of a kind that typically takes several years to conclude. And the Conservative manifesto has ruled out any extension of the so-called “transition” to full Brexit beyond the end of next year.

The leaked draft European Council conclusions, seen by The Independent, state that “negotiations should be organised in a way that makes the best possible use of the limited time available for negotiation and ratification by the end of the transition”.

The EU’s director-general for trade, Sabine Weyand, has previously warned that this timescale will only allow for a “bare bones” deal at best, with the other alternative of a no-deal Brexit.

In a press conference at the conclusion of the Nato summit in Watford, Mr Johnson was asked whether he accepted that the UK could in a year’s time be leaving the EU without a trade deal with either its former European partners or the US – and whether he had made “crystal clear” to President Donald Trump that the NHS would not be on the table in trade talks.

The prime minister responded: “I think everybody by now has rumbled this for the nonsense that it is. I think I might just wind up this press conference now because I think we have started to scrape the barrel.”

Mr Johnson later played down the difficulty of completing a free trade agreement in 11 months, telling ITV’s Robert Peston: “Have you ever known two countries start free trade negotiations or start negotiations on a new deal when they were already in perfect alignment in regulatory terms and had zero tariffs and zero quotas between them? That’s where we are.”

EU chief Brexit negotiator Michel Barnier is set to be confirmed as head of trade talks (EPA)

It was the second day in succession that Mr Johnson had ducked questions about the danger of no deal in December 2020, even though his foreign secretary Dominic Raab confirmed on Tuesday that no deal would “absolutely” be on the table in talks with the EU.

Liberal Democrat MEP Luisa Porritt told The Independent: “This leak proves the Tory pledge to ‘get Brexit done’ is a fallacy. Within 24 hours of a Johnson victory, we will be locked into a panicked negotiation about our economic future with 27 of our largest trading partners, with the clock ticking down.

“Mr Johnson has not been honest about the horrors that lie ahead of us if his botched Brexit deal is allowed to proceed.”

And Labour’s election coordinator Andrew Gwynne said: “Boris Johnson simply can’t be trusted on Brexit. There’s no chance Johnson will be able to negotiate a trade deal with the EU in a year, especially when he will be trying to sell off the NHS in a toxic trade deal with Trump at the same time.”

Mr Johnson gave his strongest hint yet that he will block Chinese tech giant Huawei from involvement in the UK’s hi-tech 5G telecoms network, in what may be an attempt to smooth the path to a US trade deal.

Just minutes after Mr Trump issued a fresh warning that Huawei posed “a security danger”, the PM said that the “key criterion” in making the decision would be “our vital national security” and the need to cooperate with UK allies.

Mr Johnson may hope that compliance with Washington’s demands over Huawei will encourage the US to accept British reluctance to open healthcare markets to American corporations.

Leaked documents released by Labour last week showed the US had made “full market access” for its companies a starting point for talks and discussed the possibility of extending drug patents in a way which would increase prices for NHS patients. But Mr Trump appears to have accepted the PM’s insistence that the NHS is not on the table, saying he would not want it even if it was offered “on a silver platter”.

President Trump cancelled a press conference during the Nato summit (AP)

A plan of action for the first 100 days of a Johnson majority government, released by the Conservatives, made no mention of the opening of talks on the UK’s future relationship with the EU or trade negotiations with Washington.

The document confirmed plans for a 19 December Queen’s Speech including bills first announced by Her Majesty on her last state opening just two months earlier. And it said a bill to ratify the EU withdrawal agreement would be introduced before Christmas and complete its passage through parliament in time for Brexit on 31 January, with a tax-cutting Budget the following month.

Outlining the plan, Mr Johnson claimed that a Tory victory would allow the UK to “finally put behind us the arguments and uncertainty over Brexit”, while failure to secure a majority would mean a hung parliament paving the way for a Final Say referendum.