Ukip's biggest donor Arron Banks has warned the party could be at an end.
The tycoon also said his close ally Nigel Farage could return again as leader to stabilise the party.
Asked if Ukip was finished, Banks told BBC Radio 4´s Today programme: "It could be, it's at a crossroads."
He expressed his doubts over whether Ukip has a future as he warned the "pressure cooker" has exploded.
Asked if Farage would come back as leader, Banks said: "I think at some point he may do, yes, maybe. In politics you can never say never, can you? It depends what happens.
"I think Nigel was probably a dominant politician of the last 20 or 30 years, and losing him has caused the pressure cooker to explode.
"I think we are struggling at the moment, there is no point in denying it.
"I don't know if it's over for Ukip. It's certainly achieved its main goal in politics, which was to get the (EU) referendum and win it.
"I think at the moment we have to wait and see if it stabilises itself and elects a credible leader. I think it's whether Nigel stays engaged with it or not."
Banks, who says he has suspended donations to the party, said he thought leadership contest front-runner Paul Nuttall lacked the "steel" to sort out the mess in Ukip.
Farage remains interim leader after Diane James quit the post following 18 days at the helm.