The former Deputy Chairwoman of UKIP has become the latest member to quit the party in protest at the leadership of Gerard Batten and his association with Tommy Robinson.
Suzanne Evans said she had become "increasingly alarmed in recent months by the perverse direction" Batten was taking the party, the day after its national executive voted against a motion of no confidence in him.
Batten has come under fire within the party in recent weeks for taking Robinson as an adviser on prison reform and rape gangs.
Last month former leader Nigel Farage said he would write to UKIP's ruling National Executive Committee to demand a vote of no confidence to remove Batten as leader, and accused him of damaging both the party and the Brexit cause.
But, on Sunday UKIP said its NEC had voted "overwhelmingly" against a motion of no confidence.
'Destroying it from within'
Former Deputy Chairwoman Suzanne Evans
Announcing her decision, Evans said that "the NEC and UKIP MEPs might be willing to turn a blind eye to the obvious attempts by Gerard and Tommy Robinson to orchestrate a 'Momentum-style' takeover of UKIP, but I am not".
She said: "I was hoping, yesterday, that sense would prevail; that UKIP's National Executive Committee would call for a 'no confidence' vote in Batten, so the party could be prevented from taking a devastatingly wrong turn.
"But if even those elected to represent ordinary members won't protect UKIP from a leader who appears hell bent on destroying it from within, then there is no hope left."
In a statement on Sunday, UKIP said that it "does not endorse the appointment of Tommy Robinson in any advisory role", adding: "He is not a UKIP member and through his associations he is barred from joining UKIP."
Batten previously defended his decision to give Robinson, whose real name is Stephen Yaxley-Lennon, a role advising him on rape gangs and prison reform, describing him as "courageous".
He attacked Mr Farage on Monday, tweeting: "Nigel Farage failed to get the UKIP MEPs to even have a vote of no confidence in me last Wed in Brussels.
"He failed to get a vote through at yesterday's NEC. Now he's reduced to doing the rounds in the MSM attacking me. My crime? UKIP isn't disappearing under my leadership."
But MEPs including Patrick O'Flynn, Bill Etheridge and William Dartmouth have all quit the party in recent months over the direction of travel within the party.