The European Union rebuffed efforts by UK premier Theresa May to renegotiate their Brexit deal on Thursday, just 50 days before Britain leaves the world’s largest trading bloc. During “robust but constructive” discussions, European Commission President Jean-Claude Juncker told the prime minister he would not re-open talks on a deal that had only been secured in December after “significant concessions” from both sides. The meetings come amid worsening relations between the two sides with senior EU leaders scathing about the approach of the leaders of the country’s Brexit faction. Donald Tusk, the European Council president, said on Wednesday there was a “special place in hell” for those who had pushed for Brexit without a plan. Mrs May’s deputy, David Lidington, told the BBC that the comments were not the “most brilliant diplomacy in the world” before Mr Tusk and other leaders met the prime minister. British MPs in January rejected Mrs May’s Brexit plan struck after months of negotiations with the EU, forcing her back to Brussels to seek further concessions. EU leaders have given few signs of giving ground to Mrs May on the key issue about the state of the border between EU member Ireland and Northern Ireland, which is part of the UK. The premier travelled to Brussels on Thursday seeking legally-binding changes to the deal to get it through the UK’s parliament but Mr Juncker said only that he would consider adding words to a non-binding political agreement. The pair agreed, however, to meet again before the end of the month to discuss the progress of efforts to secure the support of the UK parliament, according to a joint statement. A failure by Mrs May to secure any meaningful concession that can win the support of MPs increases the likelihood of a no-deal Brexit, which would see the UK crash out of the EU on March 29. The government has warned that would be the worst-case scenario for the UK, immediately scrapping trade and regulatory and political agreements and plunging the country into economic crisis. The pound fell on Thursday after Bank of England governor Mark Carney blamed Brexit uncertainty and the global slowdown for Britain facing its weakest economic growth for a decade. "The fog of Brexit is causing short term volatility in the economic data, and more fundamentally, it is creating a series of tensions in the economy, tensions for business," he said. The leader of the UK’s opposition, Jeremy Corbyn, set out his demands in a letter to Mrs May on Wednesday, which included a “permanent and comprehensive UK-wide customs union.” Mrs May has previously ruled out such a union as it would prevent the UK from running its own independent trade policy.