Suzanne Evans said Mr Bolton’s decision to end his relationship with Jo Marney would fail to save his job – urging him to quit because he had “brought the party into disrepute”.
Otherwise, next Sunday’s special meeting of Ukip’s national executive committee would pass a vote of no confidence, she predicted – plunging the party into its fourth leadership battle in just 18 months.
“He has displayed an astonishing lack of judgment,” Ms Evans said, pointing out Mr Bolton had “portrayed himself as a family man” when he won the leadership last September.
“I think he has brought the party into disrepute and, certainly, people have been kicked out of the party for that in the past,” she told the BBC’s Daily Politics programme.
She agreed that “politicians have a right to a private life”, but added: “He has left his wife for a woman who is younger than his youngest daughter, who has turned out to have held some reprehensible views.”
And, noting that the Ukip leader had ended “the romantic side” of the relationship, she asked: “Does this mean he is going to carry on taking her counsel on matters? The mind rather boggles.”
The comments laid bare the fresh turmoil at the heart of the party, which has staggered from crisis to crisis since Nigel Farage’s resignation immediately after the Brexit referendum, in June 2016.
Steven Woolfe withdrew from that battle after he was allegedly punched in the face by a fellow Ukip MEP in the European Parliament in Strasbourg, later describing the party as “ungovernable”.
At the General Election last June, Ukip won a miserable 1.8 per cent of the vote and under 600,000 votes, triggering Mr Nuttall’s resignation and a third leadership tussle.
The party then appeared to step back from the brink, when members picked Mr Bolton instead of Anne Marie Waters, a notorious anti-Islam activist, amid a threatened mass walk-out of members.
But, early on Monday, the 54-year-old Mr Bolton – asked to choose between his party and Ms Marney – announced that “the romantic side of our relationship is ended”.
However, asked if his position as leader had become untenable, he added: “First of all, I am not intending to resign - at all.”
The move came after The Mail On Sunday published texts sent by 25-year-old Ms Marney in which she said Ms Markle’s “seed” would “taint” the royal family when she wedded Prince Harry.
In one message she said she would never have sex with a “negro,” while another read: “This is Britain, not Africa”.
Ms Evans, who was deputy chairwoman until 2016, blamed Mr Farage for Ukip’s disastrous situation, warning he had “too much influence in choosing leaders”.
Noting he had backed Ms James, Mr Nuttall and Mr Bolton, she added: “His influence has meant that the wrong candidates have been selected.”
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