Commentator John Rentoul has labelled UKIP a "trainwreck" following the departure of Steven Woolfe.
Woolfe, previously a front-runner to take over the party's leadership, announced his departure in an interview with the BBC, only two weeks after an incident in the European Parliament.
He told his interviewers there was "something rotten" in the party, and that UKIP is in a "death spiral".
Rentoul, who writes for The Independent, said the party was in "terminal crisis" because it had essentially fulfilled what it had set out to do.
"What a trainwreck. This is getting worse," he told Jonny Gould and Ash. "This is a symptom of that.
"I would have thought his health is still an issue, maybe there's some sort of underlying condition exacerbated by this fracas, but I got the impression Steven Woolfe didn't want to do it and thought the party was completely dysfunctional.
"Who could disagree with him? The party is in terminal crisis because it doesn't have a purpose anymore."