Boris Johnson has refused to rule out the prospect of a no-deal exit from the EU at the end of 2020, as he abruptly drew a press conference at the Nato meeting to an end.

The Independent challenged the prime minister to say whether it was possible that the UK would reach the end of its transition to Brexit in a year’s time without sealing a trade deal with either the EU or US.

But the PM dodged the question, instead saying he was going to wind up the press conference before launching into a tirade against Jeremy Corbyn and the Labour Party.

It was the second day in succession that Mr Johnson has ducked questions about the danger that the UK will crash out of the EU on unfavourable World Trade Organisation terms at the end of next year.

Under the terms of the withdrawal deal he struck with Brussels in October, the UK has until 31 December 2020 to agree a free trade agreement (FTA) or leave with no-deal. The EU has offered to extend the negotiations to 2022, but the Conservative party manifesto explicitly rules out requesting any further delay.

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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 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Senior EU negotiator Sabine Weyand has said that the 11-month deadline leaves time at most for a “bare bones” FTA, while many trade experts believe a deal would take far longer.

At a press conference to conclude the Nato 70th anniversary leaders’ meeting in Watford, Hertfordshire, Mr Johnson was asked whether he had made it “crystal clear” to US president Donald Trump that the NHS and pharmaceuticals were off the table in any post-Brexit trade deal and whether he accepted that the UK could be leaving the EU in a year’s time without a deal with either the US or its former European partners.

He 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.”