Nigel Farage has insisted a second EU referendum is “the last thing” he wants but expressed his belief it will be “forced upon” voters.
His comments were quickly seized upon by pro-Remain supporters, while prominent Brexiteers condemned Mr Farage’s intervention.
The leading Leave campaigner later used his LBC Radio show to offer a more detailed explanation of – and an apparent backtrack on – his surprising remarks, as he urged Brexiteers to prepare for “one last dramatic battle”.
Mr Farage, who leads a group of eurosceptic MEPs in the European Parliament, claimed his meeting with the EU’s chief Brexit negotiator Michel Barnier on Monday had prompted his comments.
“I haven’t reached this conclusion comfortably or easily but my meeting with Barnier convinced me we are not going to get a good deal and Parliament isn’t going to accept it,” he said.
Mr Farage suggested, if Parliament rejected a Brexit agreement, then “both the Commons and the Lords may well do everything they can to put us through a second referendum”.
In an appeal to Brexit campaigners, Mr Farage added: “I’m saying please get yourselves ready, there may well be a second referendum on this.
“This is meant to be, actually, a wake-up call to Leavers.
“I genuinely believe we must prepare for the possibility of a second referendum whether we like that prospect or not.”
Prominent Remainers such as former prime minister Tony Blair, ex-Liberal Democrat leader Nick Clegg and Labour peer Lord Adonis have all previously called for a second Brexit vote.
Mr Farage added, if a second EU referendum were to be held, he is “confident” Leave would win with a “bigger” majority and the pro-Brussels trio would be sent “into outer space”.
But, a new ComRes poll for the Daily Mirror revealed, if there were a second EU referendum, 55% would vote to Remain and 45% to Leave.
Yet, only 43% of the 1,049 people asked were in favour of a fresh vote, with 51% opposed and 6% answering “don’t know”.
James McGrory, executive director of pro-EU Open Britain campaign, said: “It looks like the worm is starting to turn.
“In a mature democracy like ours, the will of the people can and does change and the British public have every right to keep an open mind about Brexit as new facts continue to emerge.”
Earlier on Thursday, Mr Clegg posted on Twitter: “I agree with Nigel”, while Lord Adonis commented: “Farage wants a second referendum. Bring it on!”
Downing Street insisted there will not be a second EU referendum.