UKIP leader Henry Bolton is under pressure to resign after his girlfriend was suspended by the party for apparently making racist remarks about Meghan Markle.
Jo Marney apologised in the Mail on Sunday for saying Prince Harry’s fiancee would “taint” the Royal Family and black people were ugly.
Party members are urging Mr Bolton to step aside “quickly” and “quietly”.
He has not responded but retweeted a message urging him not to quit.
Ms Marney, a 25-year-old model, claimed her texts, published by the paper, were taken out of context.
‘Considering his position’
One of the party’s MEPs said Mr Bolton, 54, should step aside “quickly”, calling him a “naive political lightweight” whose personal life was distracting from policy.
West Midlands MEP Bill Etheridge said he was not commenting on Mr Bolton’s private life but said the party had had “nothing but bad publicity” recently.
He cited several other complaints including a rise in membership fees, adding that Mr Bolton did not have the “experience or the political nous or the correct advice to deal with the issue that he faces”.
“He must go, he must go quickly, he must go as quietly as possible,” he said.
Former UKIP leadership candidate Suzanne Evans told BBC News it was “scandal after scandal with Mr Bolton”.
“I understand he is considering his position today,” she added. “We will have to see what the next few hours bring.”
UKIP activist and former leadership candidate Ben Walker said Mr Bolton should go before he destroyed UKIP’s “political family”.
The party chairman, Paul Oakden, said the leader had “some difficult decisions” to make.
“He intends on making those decisions today, and I’m sure whatever he does will be in the best interests of the party,” he told BBC’s Sunday Politics.
Mr Oakden declined to give his own views on Mr Bolton’s situation, but said the party needs to be “behind our leader 100% in taking that battle (for Brexit) forward”.
“Whether or not the party decides it is willing to give that support to Henry is for the party to decide,” he said.
The Mail on Sunday said Ms Marney sent the messages three weeks before her relationship with Mr Bolton started.
When a reply to one of her texts suggested her comments were racist, she added “so what?” and said she did not want other races invading her culture.
In a statement to the newspaper, Ms Marney said: “I apologise unreservedly for the shocking language I used.
“The opinions I expressed were deliberately exaggerated in order to make a point and have, to an extent, been taken out of context. Yet I fully recognise the offence they have caused.”
Mr Bolton earlier replied to a party member online who urged him to call for Ms Marney to have her membership removed.
“She has to go or he and @UKIP are doomed if we let this behaviour happen in the party,” the teenage activist said.
In replying, Mr Bolton tweeted: “Jo was suspended immediately upon us receiving this information.”
Mr Bolton confirmed his relationship with Ms Marney in a letter to UKIP supporters earlier this month, after splitting up with his wife.
He denied he had been involved in a “clandestine affair”.
Mr Bolton, a former army officer, took over as UKIP leader in September. If he were to quit, it would leave UKIP seeking its fifth leader in 18 months.