Britain and the EU face a “furious race against time” to agree a transition deal and future trade relations within the next 10 months, European Council president Donald Tusk has said.

In a letter to the leaders of the 27 remaining EU states ahead of a crucial summit on December 14-15, Mr Tusk urged them to show continued “unity” as Brexit negotiations enter their second phase.

Meanwhile, the European Union’s chief Brexit negotiator Michel Barnier warned there could not be any “backtracking” on the divorce deal struck between Theresa May and Brussels.

The summit is expected to agree on Friday that talks on the terms of Britain’s withdrawal have made “sufficient progress” for negotiations to move on to the future relationship.

But there are signs of lingering disgruntlement over Brexit Secretary David Davis’s suggestion the deal last week by the Prime Minister and European Commission president Jean-Claude Juncker on the issues of citizens’ rights, the Irish border and the UK’s £39 billion divorce bill was only a “statement of intent.”

Mr Barnier said the EU would be “vigilant” about any attempts by the UK to depart from the deal.

A leaked draft of the guidelines for the second phase of talks warns: “Negotiations in the second phase can only progress as long as all commitments undertaken during the first phase are respected in full.”

The European Parliament is to vote on today on cross-party amendments tabled by Brexit co-ordinator Guy Verhofstadt, warning that Mr Davis’s comment risked “undermining good faith” established in the negotiations.

Mr Davis said he and Mr Verhofstadt had agreed on the importance of last week’s joint report, adding: “Let’s work together.”