Departing Liberal Democrat leader Tim Farron | Dan Kitwood/Getty Images | Dan Kitwood/Getty Images Lib Dem leader backs second EU referendum Tim Farron says he would campaign to stay in the EU ‘on the right terms.’

The U.K.'s Liberal Democrats would actively campaign to keep Britain in the EU "on the right terms," party leader Tim Farron said Wednesday.

Farron, in Brussels for talks with Guy Verhofstadt, the European Parliament's chief Brexit negotiator, told POLITICO there was “growing support” for the party’s plan for a second referendum, in which voters would be asked to choose between any Brexit deal Theresa May gets from the EU, or simply staying inside the bloc on existing terms.

An outspoken critic of leaving the EU, Farron has positioned his party as the anti-Brexit option, calling for a referendum on any deal May's government strikes with the EU.

Asked if his party would campaign for the "stay in the EU" option in any such referendum, Farron, in an apparent hardening of the party’s pro-EU position, said: “On the right terms, yes.”

“I don’t think we should be in the euro and I wouldn’t want us to sign the Schengen agreement,” Farron said, referring to 1985 treaty creating a passport-free zone. “We want to make sure we’re pretty much on the same deal we’ve got now.”

Farron’s party currently favors a "soft Brexit," and its MPs say they will refuse to support May in triggering Article 50 unless she guarantees a second referendum and single market membership.

"There’s no deal we will get from the EU that is as good as the one we’ve currently got. It’s not to say the EU is perfect, I would want to reform it, I really would, but there are versions of Brexit that are worse than others."

The pro-EU Lib Dems have enjoyed something of a resurgence of late, after being almost wiped out at the 2015 general election when voters blamed them for forming a coalition government with the Tories.

Farron was one of just 8 Lib Dem MPs until last week when they won a by-election in the London constituency of Richmond Park after turning the vote into a ballot on Brexit. Candidate Sarah Olney overturned a 23,000 majority to win by 2,000 votes.

The Lib Dem leader has pushed for a referendum on the terms of Brexit deal to avoid a "stitch up" by the government and the EU's negotiators, none of whom “have the right to impose on the British people a deal nobody voted for.”

Farron said he was in Brussels to get clarification from the European Parliament that it will “under any and every circumstances” have a vote on the final Brexit deal.

He also sought to downplay the importance of Nigel Farage in the Brexit debate, saying the former UKIP leader represented an “insular, divided, nationalist Britain.”

“Leave may have won but Farage’s insular vision didn’t, and he didn’t speak for the majority in Britain,” Farron said. He said he found it "despicable" the assumption "that Farage speaks for the British people — he really, really doesn’t."

Asked if the recent uptick for his party could see it overtake the beleaguered Labour Party to become the main opposition to the Tories, Farron said: “Who knows? We know we have got a mountain to climb, but in some circumstances you can climb a mountain very quickly.”