Britain is giving up its presidency of the European Council next year, Downing Street has announced.
Prime Minister Theresa May informed council president Donald Tusk in a phone call on Tuesday.
The presidency rotates between the 28 EU member states on a six-monthly basis, giving each the opportunity to shape the agenda.
The UK was due to hold the seat in the second half of 2017, but Mrs May has decided that Britain should skip its turn in the light of last month's referendum vote for Brexit.
A Downing Street spokesman said that Mrs May told Mr Tusk that giving up the presidency was "the right thing to do given we will be very busy with negotiations to leave the EU".
The PM felt it was right to give other EU nations time to make arrangements for a different country to be appointed to hold the presidency during that period.
Number 10 said that Mr Tusk welcomed the fact that Mrs May had come to a swift decision on the issue.
The call was Mrs May's first conversation with the European Council president since becoming PM.