The Lib Dem leader has praised the bravery of 11 defectors from Labour and the Tories who formed the group, dubbed ‘TIG’, and raised the prospect of an electoral pact.
But shortly before announcing he would stand down, Mr Cable told The Scotsman that TIG was a flash in the pan with no prospect of winning seats in an election.
On the eve of his party’s spring conference, Mr Cable revealed he would trigger a leadership election after local elections in England in May.
Responding to polls that suggested TIG could win as much as 18 per cent of the vote in an election, Mr Cable said: “They were there for a few days and then a few days later they were back to almost zero, and we were back to where we were before.
“It was an almost completely artificial phenomenon. They’re not a party and they’re not setting up to compete against us, so it didn’t tell us anything.
“It was interesting for the journalists, but it wasn’t in any way a reflection of political currents, I don’t think.”
TIG MP Anna Soubry will attend the Lib Dem spring conference in York this weekend, sealing a close partnership based on their opposition to Brexit and support for a second referendum on EU membership.
However, sources have talked down an alliance between the two groups along the lines of the Liberal-SDP pact that eventually led to a merger and the creation of the Lib Dems.
“There is a lot of unhappiness with the present state of British politics and some people are expressing it in a quest for something new, some new movement,” Mr Cable said.
“The underlying reality is that in the British first-past-the-post system, you can’t just set up a movement and expect to have power. It doesn’t work like that. This isn’t France.
“I think at some point the political reality will kick in and there will be a recognition that until we can change it, parties will need to do what we’ve had to do, which is operate in the existing system and try and win as many seats as we can in parliament and locally.”
Lib Dem activists are set to approve party reforms that will open up leadership contests to outside figures, but Mr Cable denied a ‘celebrity’ candidate was needed to re-energise the party, which has failed to capitalise on being the first to embrace a second EU referendum. “We’ve got some very good MPs and one of them will probably take over. We shouldn’t rule out an outside talent ... but you can’t just walk in. That isn’t the intention.”