Henry Bolton has insisted he will not quit as Ukip leader and warned the party "is probably over" if he is forced out as he prepares to face down critics at a meeting of its ruling body.
The former Army officer from Kent has faced a volley of calls to resign since his now former partner was revealed to have made highly offensive comments about Meghan Markle and black people.
Ukip's national executive committee (NEC) is said to be planning to hold a vote of confidence in their leader during a special meeting on Sunday.
Mr Bolton told ITV's Peston On Sunday the party could not afford to have another leadership contest.
He added: "If the NEC decides to go down the road of months of further in-fighting and further negative media scrutiny by deciding to pass a vote of no confidence in me I think that the reality is that the party is probably over."
His comments come amid reports Nigel Farage is plotting a return to frontline British politics.
Several newspapers have reported that Mr Farage is in talks to launch a rival to Ukip if Mr Bolton steps down and the party loses its fourth leader in 18 months.
Mr Farage, who stepped down as Ukip leader in 2016, has been vocal in recent weeks about his fears about Brexit, accusing Leave campaigners of failing to adequately press the case for Britain's departure after the referendum.
He has previously said he would have "no choice" but to return to frontline politics if it appeared the Brexit he campaigned for is under threat.
The Sunday Times reports that Mr Farage has spoken to friends and held talks with multimillionaire former Ukip donor Arron Banks about launching a new pro-Brexit movement.
The newspaper says Mr Farage has been invited to be the group's president, while Mr Banks, an insurance tycoon, will be its chairman.
Ukip Treasury spokesman Jonathan Arnott left the party in protest at Mr Bolton's leadership on Friday.
He said he had "forlorn hope" when Mr Bolton was elected leader in September but it has become "abundantly clear" he is not the right person for the job.