Theresa May told another senior politician that she will set the ball rolling to leave the EU “early next year”, it emerged today.

Martin McGuinness, Northern Ireland's deputy First Minister, revealed the Prime Minister told him that Article 50 would be triggered at the start of 2017.

The claim echoes Donald Tusk, the President of the European Council, who said Ms May had given him a similar briefing when the pair held talks at No 10 earlier this month.

Boris Johnson goes 'off script' about when Brexit should happen

However, Downing Street has refused to give what it calls a “running commentary” on its timetable and slapped down Boris Johnson, the Foreign Secretary, for pointing to January.

Speaking at a fringe event at the Labour conference in Liverpool, Mr McGuinness, of Sinn Fein, said: “I asked her about when she will trigger Article 50 of the Lisbon Treaty [and she said] that she was going to do it not this year but very early next year.

“So we are working on the basis that early next year, the article will be triggered,” the Politics Home website reported him saying.

What experts have said about Brexit Show all 11 1 /11 What experts have said about Brexit What experts have said about Brexit Chancellor of the Exchequer Philip Hammond The Chancellor claims London can still be a world financial hub despite Brexit “One of Britain’s great strengths is the ability to offer and aggregate all of the services the global financial services industry needs” “This has not changed as a result of the EU referendum and I will do everything I can to ensure the City of London retains its position as the world’s leading international financial centre.” Reuters What experts have said about Brexit Yanis Varoufakis Greece's former finance minister compared the UK relations with the EU bloc with a well-known song by the Eagles: “You can check out any time you like, as the Hotel California song says, but you can't really leave. The proof is Theresa May has not even dared to trigger Article 50. It's like Harrison Ford going into Indiana Jones' castle and the path behind him fragmenting. You can get in, but getting out is not at all clear” Getty Images What experts have said about Brexit Michael O’Leary Ryanair boss says UK will be ‘screwed’ by EU in Brexit trade deals: “I have no faith in the politicians in London going on about how ‘the world will want to trade with us’. The world will want to screw you – that's what happens in trade talks,” he said. “They have no interest in giving the UK a deal on trade” Getty What experts have said about Brexit Tim Martin JD Wetherspoon's chairman has said claims that the UK would see serious economic consequences from a Brexit vote were "lurid" and wrong: “We were told it would be Armageddon from the OECD, from the IMF, David Cameron, the chancellor and President Obama who were predicting locusts in the fields and tidal waves in the North Sea" PA What experts have said about Brexit Mark Carney Governor of Bank of England is 'serene' about Bank of England's Brexit stance: “I am absolutely serene about the … judgments made both by the MPC and the FPC” Reuters What experts have said about Brexit Christine Lagarde IMF chief urges quick Brexit to reduce economic uncertainty: “We want to see clarity sooner rather than later because we think that a lack of clarity feeds uncertainty, which itself undermines investment appetites and decision making” Getty Images What experts have said about Brexit Inga Beale Lloyd’s chief executive says Brexit is a major issue: "Clearly the UK's referendum on its EU membership is a major issue for us to deal with and we are now focusing our attention on having in place the plans that will ensure Lloyd's continues trading across Europe” EPA What experts have said about Brexit Colm Kelleher President of US bank Morgan Stanley says City of London ‘will suffer’ as result of the EU referendum: “I do believe, and I said prior to the referendum, that the City of London will suffer as result of Brexit. The issue is how much” What experts have said about Brexit Richard Branson Virgin founder believes we've lost a THIRD of our value because of Brexit and cancelled a deal worth 3,000 jobs: We're not any worse than anybody else, but I suspect we've lost a third of our value which is dreadful for people in the workplace.' He continued: "We were about to do a very big deal, we cancelled that deal, that would have involved 3,000 jobs, and that’s happening all over the country" Getty Images What experts have said about Brexit Barack Obama US President believes Britain was wrong to vote to leave the EU: "It is absolutely true that I believed pre-Brexit vote and continue to believe post-Brexit vote that the world benefited enormously from the United Kingdom's participation in the EU. We are fully supportive of a process that is as little disruptive as possible so that people around the world can continue to benefit from economic growth" Getty Images What experts have said about Brexit Kristin Forbes American economist and an external member of the Monetary Policy Committee of the Bank of England argues that the economy had been “less stormy than many expected” following the shock referendum result: “For now…the economy is experiencing some chop, but no tsunami. The adverse winds could quickly pick up – and merit a stronger policy response. But recently they have shifted to a more favourable direction” Getty

The Prime Minister has said she will not begin the formal two-year leaving process before the end of this year, but has stopped short of saying exactly when it will happen.