But the ex-Army officer was boosted by ex-leader Nigel Farage who backed his call to “drain the swamp” in the party.
However, Mr Farage refused to give Mr Bolton, 54, his personal backing and said he had a month to make his case to stay as leader.
East Midlands MEP Jonathan Bullock quit as energy spokesman of the party in protest at the “close relationship” of Mr Bolton and Jo Marney, 25, who caused fury over racist texts she sent about Prince Harry’s girlfriend Meghan Markle.
Mr Bullock said he could not serve under a leader who had a relationship with someone who had “obnoxious views”.
He added: “This has become a modern-day Profumo scandal. It has politics, sex, a model, even the Royal Family has been brought in. The only thing missing is a Russian spy.”
Mr Bolton received a unanimous vote of no confidence by Ukip’s national executive and now faces a meeting of the party’s membership