UK’s exit from the European Union: May-day on March 29

But while Britain is keen to secure a free trade trade deal with the EU as part of the exit negotiation process, the European Council insists it won’t discuss any such trade relationship until the United Kingdom agrees to an expensive separation fee. I have also been clear that as we leave the European Union I will work to deliver a deal that works for the whole of the UK.

Notification of the historic step will come in the form of a letter from the Prime Minister to Mr Tusk, though Downing Street did not make clear whether this would be a physical letter handed to the European Council president by a United Kingdom representative or might be sent electronically.

The U.K. on Monday announced that it will trigger Article 50 and officially begin divorce talks on March 29.

For her part, May “sends her very best wishes” to her EU colleagues, the British premier’s spokesman said, adding: “The EU 27 are moving in one direction, the British public voted to go in another direction”.

The European Commission’s Brexit negotiator Michel Barnier has said they must be wrapped up by October 2018 to give the EU and national parliaments time to ratify the deal. Priority must be certainty, clarity for all: “citizens, companies and member states”, Tusk tweeted.

Within 48 hours of Mrs May’s move, Donald Tusk, the European Council president, will write to the EU’s remaining 27 members to summarise the guidelines for Brexit.

The former French government minister said the talks will be transparent and open, saying that “these negotiations can not take place in secret”.

Labour MP Pat McFadden, a leading supporter of the Open Britain group, said: “As she enters talks with our European partners, it is up to the Prime Minister to deliver the deal that she and her ministers have promised”.

Michel Barnier, who will be leading the European Union side during the Brexit discussions, said there could be “total uncertainty” for Britain if no deal is secured in that timeframe.

Britain has said it wants to agree its divorce and a new relationship with Europe within the two years. This means the UK’s membership of the European Union will end on 29 March 2019.

Lib Dem leader Tim Farron, who has called for the public to have their say on the terms of exit in a further referendum, said Mrs May’s decision to rule out membership of the single market before negotiations began was proof she was pursuing an “extreme and divisive” Brexit.

Abe, in Brussels to push an EU-Japan trade deal, urged the EU and Britain to ensure a smooth “transition period”.

Mr Tusk’s decision to hold the summit between the first and second rounds of the presidential elections in France will be unwelcome news to French officials.

European Union leaders gather in Rome this week to proclaim their “common future” on the bloc’s 60th birthday, despite a wave of crises including Britain’s looming exit from the bloc. May has already announced she will not be attending the event.