Britain will not take up its scheduled presidency of the EU Council next year and will instead focus on its preparations to leave the bloc, Theresa May has said.
The announcement is the first key responsibility relinquished by Britain in the wake of the EU referendum result.
The move came to light in a phone call on Tuesday between the new Prime Minister and the council president Donald Tusk.
The presidency of the council rotates on a six-montlhy basis, offering each of the EU's 28 member states the opportunity to shape the EU's agenda. Slovakia is the current president, with Estonia set to follow the UK's slot.
Functionally it chairs meetings of the Council, where ministers and heads of states meet. It also determines its agendas, and sets a programme of work for the six month period.
The UK was due to take over for the second half of 2017, but it is possible that Ms May will by that point have triggered Article 50 of the Lisbon Treaty, beginning the formal multi-year process of Brexit.
The country that will take Britain's vacated place in the presidency is yet to be determined. The presidency is not individual and is held by the whole country, with a different representative depending on the particular sitting of council.
In a statement, a Downing Street spokesperson said: “The President of the European Council Donald Tusk called the Prime Minister yesterday evening to congratulate her on her appointment.
“The Prime Minister thanked President Tusk for the clear message he has given that the UK remains a full member of the EU until such a time as we leave and the Prime Minister underlined that she wants to approach the negotiations on the UK’s exit from the European Union in a constructive and pragmatic spirit.
“In this context, the Prime Minister suggested that the UK should relinquish the rotating Presidency of the Council, currently scheduled for the second half of 2017, noting that we would be prioritising the negotiations to leave the European Union.
“Donald Tusk welcomed the PM’s swift decision on this issue which would allow the Council to put alternative arrangements in place.
“Finally, the Prime Minister explained that we will need to carefully prepare for the negotiations to leave the EU before triggering Article 50. Donald Tusk reassured the Prime Minister that he will help to make this process happen as smoothly as possible.
“They concluded by looking forward to a strong working relationship and agreed that they should meet soon in Brussels or London.”
Brexit reactions – in pictures
Brexit reactions – in pictures
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Leave supporters cheer results at a Leave.eu party after polling stations closed in the Referendum on the European Union in London
Mr Cameron announces his resignation to supporters
Donald Tusk proposes that the 27 remaining EU member states ‘start a wider reflection on the future of our union’
Ukip leader Nigel Farage greets his supporters on College Green in Westminster, after Britain voted to leave the European Union
Supporters of the Stronger In Campaign react as referendum results are announced today
Boris Johnson leaves his home today to discover a crowd of waiting journalists and police officers
Leave EU supporters celebrate as they watch the British EU Referendum results being televised at Millbank Tower in London
Supporters of the Stronger In Campaign react as results of the EU referendum are announced at the Royal Festival Hall
Supporters of the Stronger In campaign react after hearing results in the EU referendum at London's Royal Festival Hall
The call was Ms May's first conversation with the European Council president since becoming Prime Minister.
It comes days after the new Foreign Secretary Boris Johnson paid his first overseas visit to Brussels.
Mr Johnson met European leaders and US secretary of state John Kerry. They discussed the current situation in Turkey, the Nice attacks, as well as the fundamentals of Britain leaving the European Union.