Sir Vince Cable has said a second referendum should be mandatory if Scotland ever voted to leave the UK, so that any terms of Scottish independence agreed could be confirmed by the voting public as acceptable.
The Liberal Democrat leader pointed to “confirmatory” votes in countries like Switzerland, where such ballots are common.
He also urged the SNP to “come off the fence” on a second EU referendum.
Speaking to BBC Scotland, he said: “If there ever were in future a referendum on Scottish independence and people voted for it, I think they would themselves have to accept that there should then be a confirmatory vote at the end.
“That would be the way referendums are conducted in places like Switzerland, which use these things commonly.
“So I don’t think there’s any inconsistency with (the SNP) supporting us on the principle of having a people’s vote on Europe.”
Both the Lib Dems and SNP want to keep the UK in the single market and customs union, but Nicola Sturgeon has not endorsed holding a second vote on any Brexit deal.