Party shaken by resignation
James quits as UKIP leader after just 18 days
She was elected to replace Nigel Farage at the party’s Bournemouth conference, but told her Twitter followers she has stepped down for “personal and professional reasons”.
Mr Farage, who insisted he did not want to make another comeback, has agreed to become interim leader until a permanent successor is elected.
There has been speculation that Ms James, an MEP, had been bounced into the role. She did not appear on the BBC’s Question Time programme last week and was replaced by fellow MEP Steven Woolfe.
In a statement, she said: “It is great regret that I announce that I will not be formalising my recent nomination to become the new Leader of the party.
“I have been in discussion with party officers about the role. It has become clear that I do not have the 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.”