Ukip in turmoil as leader Diane James quits after just 18 days

Ms James cited "personal and professional" reasons for her decision, saying that she had not been given sufficient authority to force through changes she wanted to make to the party.

It is also thought that her husband's ill-health and a recent incident in which she was "badly shaken up" after being verbally abused and spat at in a central London street may have played a role in persuading her to step down.

Confusion surrounded her position after she suggested in a statement that she had never formally taken up the role of leader after winning a landslide victory in the race to succeed Nigel Farage on September 16.

Party sources questioned her claim that the election amounted only to a "nomination" as leader which needed to be registered with the Electoral Commission to be formally confirmed.

Ukip's ruling National Executive Committee is expected to hold an emergency meeting within days to choose an interim leader and agree a timetable for the second leadership election within weeks.

Bookmakers installed North-West England MEP Steven Woolfe - who was barred from standing to replace Mr Farage after handing nomination papers in 17 minutes late - as hot favourite, followed by Suzanne Evans, who missed out on the chance to run because of a suspension which has now been lifted.

In her brief time as leader, Ms James had not appointed a deputy, so there is no one in place to act as a stand-in while a new election is arranged. Party officials were unable immediately to say who was leading the party.

Mr Farage poured cold water on speculation he might return to lead the party for a third time, after stints from 2006-09 and 2010-16, telling the Press Association: "Not for 10 million dollars."

And asked if he would take 20 million dollars, he said: "No, I'm not coming back, I'm retired."

Ukip chairman Paul Oakden said on Tuesday: "It is with regret that I have tonight received confirmation that Diane James has chosen to resign as party leader, citing personal and other reasons. I will now look to convene an emergency meeting of our NEC to confirm the process for electing Diane's replacement.

"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."

It is understood that Mr Oakden was not informed in advance of Ms James's intention to quit, and received formal confirmation only when she released a statement on Twitter.

In a statement announcing her decision, Ms James said: "It is with great regret that I announce that I will not be formalising my recent nomination to become the new leader of the party with the Electoral Commission.

"Having won the enthusiastic support of party members, I was nominated by them as the new leader at the recent Ukip Bournemouth conference.

"Since that time, I have been in discussion with party officers about the role. 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 electoral process further."

Ukip insiders questioned suggestions that Ms James had failed to receive support from officials.

The 56-year-old former Conservative councillor, who defected to Ukip in 2011, said she would stay on as an MEP for South-East England.

Elected to the European Parliament in 2014 after achieving national prominence as second-placed candidate in the 2014 Eastleigh by-election, Ms James was the party's first woman leader and won the post by a wide margin after winning the backing of senior Ukip figures including Mr Farage.

But questions were raised about her commitment to the post after she declined to take part in hustings debates around the country with rival candidates.

In September's election, Ms James took 8,451 out of the 17,970 votes cast, romping home ahead of Lisa Duffy - backed by many in the anti-Farage wing of the party - Bill Etheridge, Phillip Broughton and Elizabeth Jones.

In her acceptance speech, she promised to bring a new professionalism to the party, saying: "We are going to confound our critics, we are going to outwit our opponents, we are going to build on our election success that we have achieved to date and do more."

Ukip's only MP, Douglas Carswell, declined to comment on Ms James's resignation, saying in a tweet: "In the middle of supper. Not taking calls about UKIP stuff. It's shepherds pie, by the way."

Mr Etheridge said he was "very disappointed" the leader had stepped down, describing her statement as "peculiar".

The MEP told ITV's Good Morning Britain: "Unfortunately, Diane has stood down and the reasons for that are pretty unclear to me."

Speaking from Strasbourg, he added: "That's rather a peculiar statement that she's made because, as far as I'm aware, being out here with MEPs and colleagues, we've all been ready and willing to help and support her in what she wanted to do.

"She won the election fair and square and we were all ready to back her."

Mr Etheridge, a runner-up in the leadership race, added that he would not rule out standing again for leader.

Scottish Conservatives leader Ruth Davidson said Ms James's resignation showed Ukip is a "shambles".

She told ITV's Good Morning Britain: "I have to say I was surprised when I heard the news last night. I thought Sam Allardyce was holding the record this week for resignations but it turns out that Diane James has taken his crown.

"I think you need to look around the political environment in the UK at the moment, and we saw last week in Liverpool the Labour Party riven with divisions, talking to itself and not the country, you see Ukip as a shambles over the summer, a shambles now with their leader not even lasting three weeks.

"And there really is an incumbency on the Conservative Party, the party of government, that sense of duty, that sense of service that the Prime Minister embodies so well, that we do talk for the country."

Mr Oakden said Mr Farage could still be listed as the registered leader of the party if the Electoral Commission has not received Ms James's paperwork following her election win.

He told BBC Radio 4's Today show: "If they still have Nigel Farage down as the leader it's going to make it a very interesting day for me, I suspect."

He added: "He has the party at his core and he will do as he has always done - whatever is in the best interests of Ukip - and he will be ready to serve it, I have no doubt, in whatever way he can, in what, let's face it, are going to be a challenging couple of months."

He said it is "very unlikely" Mr Farage would return to lead the party again, but added: "I wouldn't say anything is impossible right now."

Mr Oakden said he had not spoken to Ms James about her decision, but insisted it was "unfair to characterise this as an issue between Diane and the NEC".

"Frankly, I'm not certain as to which party officers she's referring to - I can only speak for my part and the part of the NEC which is they were as constructive as they could be under the circumstances of a new leader being elected," he said.

Ms Duffy said she understood Ms James had written "under duress" in Latin on her registration forms when taking over as leader.

"My understanding is that is what's happened, but I haven't got proof myself," she said.

The former party director said she was not surprised Ms James had stood down so quickly, after offering no leadership over the past few weeks.

She told BBC Radio 4's Today show: "I didn't believe this was something that she particularly wanted to do or had the passion to do. So I'm not surprised."

Ms Duffy said she would not rule herself out from running in another leadership election.