The Liberal Democrat leader, Sir Vince Cable, has denied he was discussing the creation of a new anti-Brexit centrist party at a private meeting on Monday that led to him missing tight votes in the House of Commons.

He also ruled out joining or merging with another party, and said he had repeatedly warned those disillusioned with the current political parties that the UK’s first past the post electoral system makes setting up a new party “often suicidal or silly”.

But, in an interview on Pienaar’s Politics on BBC Radio 5 Live, Cable refused to discuss who else attended what he described as “a confidential private discussion”, or exactly what they talked about.

Attending the dinner on Monday meant Cable missed two votes on Brexit legislation, each of which the government won with majorities of just three. Tim Farron, the former Lib Dem leader, was also absent.

It is understood that no MPs from other parties, and no donors, were at the dinner, where Cable and others were engaged in a wide-ranging discussion on how Brexit was contributing to a realignment in UK politics – an issue of particular interest to the Lib Dem leader.

In his interview, Cable said reports claiming the creation of a new centre-ground party was discussed at the dinner were “not correct”. But he defended talking to people in other parties, saying it was “part of the job”.

Without going into details of what was discussed, Cable said he was sceptical of the case for setting up a new party.

“I warn people who go around talking about new parties that under the first past the post system this is often suicidal and silly, and we’ve seen quite a lot of new parties being launched recently, and [they’ve] crashed and burned very quickly,” he said.

“It’s much better to work constructively with people in other parties.”

Asked if he would ever join a new party, he said he would not “because I’ve got a very good party of my own which is winning some of the key arguments”. But he said he was in favour of parties collaborating, as the Lib Dems and the Greens did in Richmond, his local council, where they struck a deal over seats at the local elections.

Cable said his priority was to work with other parties to stop Brexit but that in the longer term he expected to see a realignment of politics.

He continued: “The tensions building up in the Labour party and the Conservative party are so severe that it’s difficult to see them surviving in their present form, and we have to think ahead a little bit. And my party will play a key role in whatever happens.”

In his interview, Cable described as “ridiculous” claims that his leadership of the Lib Dems was at risk. Some Lib Dem activists are reportedly planning to discuss replacing Cable at a meeting this week, but Cable dismissed the notion that his position was under threat, saying this was “the last thing” he was worried about.

“Unlike Theresa May and Jeremy Corbyn for different reasons, I’m in the fortunate position of having a united, cohesive team of people,” he said. Under his leadership, the party was going forward, he said.

“It’s not spectacular, but I think we’ve made very good, solid progress, and my colleagues recognise that. And we’ve had record levels of membership which has held up and is still growing, as far as I’m aware. So it’s a good story.”