Former Ukip leader Diane James is the latest MEP to quit the party after the Brexit vote and Nigel Farage's resignation.
James, who served as the head of the Eurosceptic party for just 18 days from 16 September, said she took the decision to sit as an independent in the European Parliament because her relationship has become "increasingly difficult".
"At a high proﬁle public event in Cambridge last week, I was asked why I had not completed the process to become leader of UKIP?" the 57-year-old said in a statement released on Monday (21 November).
"I had little option, but to give the truthful response that, although nominated leader by popular vote in the membership, I found that I had no support within the executive and thus no ability to carry forward the policies on which I had campaigned.
"My decision to retire from the election process and not complete it was very difﬁcult personally and professionally, given that UKIP has dominated my life and all my efforts for over five years.
"In recent weeks, my relationship with the party has been increasingly difﬁcult and | feel it is now time to move on. I wish the party well for the future under new leadership."
James' resignation comes after Ukip's former migration spokesman Steven Woolfe quit the party in October. Woolfe, a former leadership favourite, was left hospitalised after an "altercation" with fellow MEP Mike Hookem in the European Parliament in Strasbourg.
European Parliament President Martin Schulz launched an investigation into the incident, while a probe from Ukip led to Hookem being reprimanded.
Ukip will unveil a new leader on 28 November, with former deputy leader Paul Nuttall, former deputy chair Suzanne Evans and former parliamentary candidate John Rees-Evans left in the contest.
Farage, Ukip's interim leader, met with US President-elect Donald Trump at Trump Tower, New York, on 12 November after his White House victory.
UPDATE: 16:53 GMT
Farage and Evans have called on James to resign as an MEP. "This is yet another act of irrational selfishness from Diane James. This pattern of behaviour says that she is unfit to continue as an MEP. She should do the honourable thing and resign," Farage said.