Diane James has quit as Ukip leader after just 18 days.
The MEP was elected to replace Nigel Farage as leader last month, but stepped down late on Tuesday night.
In a statement, James said: “It has become clear that I do not have sufficient authority, nor the full support of all my MEP colleagues and party officers to implement changes I believe necessary and upon which I based my campaign.
“For personal and professional reasons therefore, I will not take the election process further.”
She added: “I will continue to concentrate fully on my activities and responsibilities as an elected Ukip Member of the European Parliament for the South East region.”
Ukip chairman Paul Oakden said an “emergency meeting” of the party’s ruling NEC would now be held to discuss electing a replacement leader.
He said: “Whilst the decision is unfortunate, it is one that Diane is entitled to make. We thank her for all her work as leader, and as a hard working MEP, a role she will continue with her customary vigour”.
Speaking on BBC Radio 4’s Today programme this morning, Oakden denied his party had become a joke.
“I wouldn’t call it a farce,” he said, “it’s an unfortunate situation but it’s one that our party are more than capable of dealing with.”
On Monday, the Electoral Commission confirmed to HuffPost UK it had not received the paperwork from Ukip confirming James was the party’s new leader - meaning Nigel Farage is technically still in charge.
A spokesperson said: “We have been in contact with UKIP and are expecting the party’s leadership change to be confirmed shortly.”
Several Ukip sources told HuffPost UK James did sign the forms but added the words “under duress” in Latin underneath her signature, rendering it void.
James was overwhelming elected to succeed Farage by Ukip members on September 16, but her campaign was dogged by rumours that she was reluctant to stand.
She refused to take part in any of the leadership hustings, and instead held her own campaigning events.
After becoming leader, rumours persisted that she was not approaching the job with enthusiasm, and had made little effort to reach out to the party’s MEPs.
One Ukip source told HuffPost UK she pulled out of appearing on the BBC’s Question Time programme last week and had to be replaced by fellow MEP Steven Woolfe.
Douglas Carswell, Ukip’s only MP, initially refused to be drawn on the matter as he was eating a shepherds pie.
He later told HuffPost UK: “I’m sad and surprised. I just hope she’s alright.”
It is unclear who is now leading Ukip, as James did not appoint a Deputy after Paul Nuttall stood down from the role.
However, it appears Farage has ruled out a comeback.