A No 10 source has said a Brexit deal is "essentially impossible" after a call between the PM and Angela Merkel. Boris Johnson and the German chancellor spoke earlier about the proposals he put forward to the EU - but the source said she made clear a deal based on them was "overwhelmingly unlikely". The BBC's Adam Fleming said there was "scepticism" within the EU that Mrs Merkel would have used such language. And the EU's top official warned the UK against a "stupid blame game". President of the European Council Donald Tusk sent a public tweet to Mr Johnson, writing: "What's at stake is not winning some stupid blame game. At stake is the future of Europe and the UK as well as the security and interests of our people." Ireland's Tánaiste (Deputy Prime Minister), Simon Coveney said a deal was still possible but "not any at cost" - and the UK must accept it had "responsibilities" on the island of Ireland. Mrs Merkel's spokesman said her office would not reveal details of "private, closed" conversations. But Norbert Rottgen, an ally of the chancellor who is chair of the Bundestag's Foreign Affairs Committee, said there was "no new German position". He tweeted that a deal based on the UK's latest proposals had "been unrealistic from the beginning and yet the EU has been willing to engage". The BBC's Europe editor Katya Adler said it was "no secret" Berlin found the UK's proposed new customs solution for Northern Ireland problematic, but it had not yet given up hope. There has been little sign of progress in talks between the two sides since Mr Johnson sent new proposals for a deal to Brussels last week, with the EU demanding "fundamental changes". Officially, the prime minister's spokesman said the talks - aimed at securing an agreement at next week's EU summit - were "at a crucial point", but denied they were over. Scotland's First Minister and leader of the SNP, Nicola Sturgeon, said Downing Street's response to the phone call was an "attempt to shift the blame for the Brexit fiasco". And Labour's shadow Brexit secretary Sir Keir Starmer told MPs the government was "intent on collapsing the talks and engaging in a reckless blame game". "The stark reality is the government put forward proposals that were designed to fail," he said, adding that it was "beneath contempt" that, according to a Downing Street source reported by the Spectator, the UK could withdraw security co-operation from other EU countries if it were forced to remain beyond 31 October. The PM has insisted the UK will leave the EU on that date, with or without a deal. That is despite legislation passed by MPs last month, known as the Benn Act, which requires Mr Johnson to write to the EU requesting a further delay if no deal is signed off by Parliament by 19 October - unless MPs agree to a no-deal Brexit. The key focus of the new UK plans is to replace the so-called backstop - the policy negotiated by Theresa May and the EU to prevent a hard border returning to the island of Ireland - which has long been a sticking point. After presenting them, government sources hoped the sides might be able to enter an intense 10-day period of talks almost immediately, but a number of senior EU figures, including Irish Taoiseach Leo Varadkar, warned they did not form the basis for deeper negotiations - even if they believed a deal could still be done. The No 10 source said Tuesday morning's phone call - which was not discussed at cabinet - had been a "clarifying moment", adding: "Talks in Brussels are close to breaking down, despite the fact that the UK has moved a long way." The UK's chief negotiator, David Frost, is continuing to meet EU counterparts in Brussels, but one European official said he had so little room for manoeuvre, it called into question whether Britain was serious about getting a deal.