Guy Verhofstadt said he believed the UK would one day come back to “the great European family”, despite its looming departure.
He made the prediction in a debate of MEPs about the withdrawal agreement, in which chief negotiator Michel Barnier reaffirmed that “this deal is the only one and the best possible” for the UK.
Mr Verhofstadt told the parliament: “Let me make clear that in this process there are no winners. The departure of the UK from the European Union is a failure for everybody, for the UK, as for the EU.
“Last Sunday was a sad day for both. So let us make the best of it, in the knowledge that once, in the near future there will be a new generation in Britain who will decide to come back into the great European family.”
Polls and studies suggest that young people were significantly more likely to vote Remain than the older generation.
Other senior MEPs speaking during the debate backed the deal. Elmar Brok, a German MEP from Angela Merkel’s Christian Democratic Union, warned Remainers in the UK that they would be taking a risk by rejecting the plan.
“If there is no treaty then there will be no transitional period and it’s going to be an abrupt break,” he said.
“It must be made clear that it is a very risky initiative for the Remainers, rejecting this and hoping something else is going to come, like a referendum – that’s a very risky business.”
He added that the EU had “got the best deal possible”, adding: “Brexit is a very bad affair for the European Union and Great Britain – more for Great Britain, given its size, but it’s also a very bad thing for us as well.”
Philippe Lamberts, a Green MEP who sits on the parliament’s Brexit steering group, said “no other Brexit is available” and that a no-deal Brexit would “make the UK a rogue state, a country whose signature with any other partner would amount to just nothing”.
“The real choice is between Brexit under the terms negotiated and no Brexit at all,” he said, adding that the EU should allow Britain to stay in if it wanted to.
Former Ukip leader Nigel Farage said: “I’m in no doubt that this withdrawal agreement is a good deal … it’s a good deal for the European Union. For the UK I think it’s probably the worst deal in history.
“Mr Barnier, I have to say to you: I wish you were on our side, really. Because it’s game set and match to you. You probably can’t even believe your luck that you came up against a British prime minister who met every single demand of yours while at the same time trying to deceive the British public.”
Mr Barnier, the EU’s chief negotiator, echoed his message from Sunday’s European Council summit to MEPs.
“Given the difficult circumstances of this negotiation and given the extreme complexity of all the issues of the British withdrawal, the deal that is on the table ... this deal is the only one and the best possible,” Mr Barnier said. “Now is the time for ratification.”
He added: “It’s not a question of winners and losers because Brexit is a lose-lose. There is no added value.”
EU leaders signed off the withdrawal agreement, which has taken 18 months to negotiate, at a summit in Brussels on Sunday. Theresa May now faces an uphill struggle to get the plan through parliament.
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