Liberal Democrat grandee Sir Vince Cable, the former business secretary, has been caught out calling for the party's supporters to vote tactically at the general election on 8 June.
The recording of Cable, published by LBC and Sky News, will prove embarrassing for Liberal Democrat leader Tim Farron, who has ruled out a coalition deal with Jeremy Corbyn's party.
"I'll just give one example – there's [Labour's] Rupa Huq who's the candidate in Ealing I think," Cable said.
"Purely by coincidence I found myself, I think it was on Any Questions or one of those programmes in Warwick a few months ago, and I gave her a lift home back to Ealing.
"We talked for a couple of hours, and it was very clear that on almost every issue our views were almost identical.
"And so I would find it difficult to vote against somebody like that, and I hope that our people around the country are discriminating and think and act in a constructive way."
The comments also play into the Conservative claim that the UK faces a "coalition of chaos" between Farron, SNP leader Nicola Sturgeon and Corbyn.
Cable is hoping to win back his old London seat of Twickenham at the election. Conservative Tania Mathias won the Remain-backing constituency in 2015 with a majority of more than 2,000 votes.
The Greens, who won 4% of the vote in 2015, are currently fielding a candidate against Cable and Mathias. But a senior party source has told IBTimes UK that could change since co-leaders Caroline Lucas and Jonathan Bartley have back an anti-Tory "progressive alliance".