Former British foreign minister David Miliband called for voters to be given a second referendum on whether Britain should leave the European Union.

Writing in the Observer newspaper Miliband, foreign minister under a Labor government between 2007 and 2010, called Brexit an "unparalleled act of economic self-harm" and said there should be another public vote once the final terms of Britain's exit are known.

Although no longer a serving British politician, Miliband - brother of former Labor leader Ed Miliband - is still seen as an influential centrist voice. His criticism joins that of a growing number of pro-EU figures from across the political spectrum who say Prime Minister Theresa May's Brexit strategy is economically damaging and that voters should be given a chance to halt the process.

Meanwhile, the British government tried to fight back against criticisms that it is divided and unprepared for Brexit, saying it will set out detailed plans for the U.K.'s exit from the European Union and issuing a joint statement by two Cabinet rivals over Europe.

Trade Secretary Liam Fox, a strong supporter of leaving the European Union, and the more pro-EU Treasury chief Philip Hammond, wrote in the Sunday Telegraph that they agreed there should be a "time-limited" transition period after Britain formally leaves the bloc in 2019, to avoid a "cliff-edge" for people and businesses.

The government also said Sunday it wants to increase pressure on the 27 other EU nations to start negotiating a "deep and special" future relationship that would include a free trade deal between Britain and the EU. The push comes after EU officials expressed impatience with the pace of Britain's preparations.