Alistair Carmichael, the Lib Dem chief whip, said a broader message was needed to tap into buoyant support for Jeremy Corbyn’s Labour Party.
And he suggested a national conversation like the Scottish Constitutional Convention that delivered the vote for devolution 20 years ago this week was needed before asking voters to reconsider the UK’s place in Europe.
The comments follow criticism of the Lib Dem strategy in June’s general election from new leader Vince Cable, who has sought to pivot focus onto economic inequality. Another Lib Dem grandee, the former leader Paddy Ashdown, this week called on his party to “return to being radical”.
Mr Carmichael said a “referendum on the facts” of the UK’s eventual Brexit deal was central to his party’s policy and would gain traction as Brexit unfolds.
But he said the party’s four Scottish MPs, who now make up a third of the Westminster group including deputy leader Jo Swinson, were conscious that the Lib Dems must “beware the neverendum”.
“One of the other lessons we have to learn from the general election is there is a finite appetite for talking about Brexit and the constitution,” Mr Carmichael said.
“That is part of what is now causing difficulties for the SNP in Scotland. However Brexit develops, people still want to see improvements in health, education, housing, transport, policing, the rest of it.
“We’ve always been candid that the strategy of having a second referendum on the deal is not ideal. If we were to plot our way forward, we wouldn’t necessarily start from here, but we are where we are.”
Mr Carmichael said the campaign for devolution provided the blueprint to change opinion on Europe and secure broader reforms like the abolition of the House of Lords and a federal UK.
“That’s the only way you can ever achieve constitutional reform, by building a consensus. We have to look at how we use referendums in a parliamentary democracy because actually, 55-45 or 52-48, what does that really tell you?
“It tells you your country is split down the middle. If you want to achieve constitutional change, you have to do what we did in the 1990s - a constitutional convention, broad based support, bring in people beyond political parties, like the churches and the trade unions, civic groups - so that when you actually get to the point of having a referendum as we did in 1997, it was something that legitimized a decision that was being made, validated it, rather than a tool for making the decision itself.”