Ukip leadership hopeful Steven Woolfe, the previous frontrunner in the race to succeed Nigel Farage, has been excluded from the contest, the party said.
The North West MEP and Ukip's migration spokesman had been the bookies' favourite to take the top job but was disqualified after he was 17 minutes late submitting his nomination papers.
Supporters claimed he had been the victim of a coup led by Ukip's only MP, Douglas Carswell, and Neil Hamilton, group leader in the Welsh Assembly.
The ruling National Executive Committee voted to block his candidacy by a "clear majority", a spokesman said.
MEPs Bill Etheridge, Diane James and Jonathan Arnott, along with Ukip’s deputy chair in Lambeth Elizabeth Jones, Councillor Lisa Duffy, and Phillip Broughton will all be on the ballot paper.
There were also questions over whether Mr Woolfe would be eligible to stand following allegations he allowed his membership of the party to lapse for 15 months.
However, officials said that this had no bearing on their decision to exclude him from the race.
A Ukip spokesman said: "By a clear majority of NEC members, Steven Woolfe MEP's application was considered to be ineligible as a result of a late submission and as such he did not meet the eligibility criteria. His membership of the party was not in question."
Mr Woolfe was tipped to win the leadership, and had the backing of influential Ukip donor Arron Banks, who is close to Mr Farage, but he missed the deadline to submit his nomination application on Sunday, blaming technical difficulties.
It also emerged that he failed to declare a drink-driving conviction when he stood for a police and crime commissioner post in 2012.
The MEP said he "forgot about the conviction" when he stood in the Greater Manchester PCC election in 2012, in a possible breach of electoral law.
He has also denied allegations that he allowed his membership to lapse in 2014, which raised issues about his eligibility under controversial new party rules.
Mr Woolfe said he was "extremely disappointed" by the decision and branded the NEC "not fit for purpose".
He said: "Over the course of this leadership election, the NEC has proven it is not fit for purpose and it confirmed many members' fears that it is neither effective nor professional in the way it governs the party.
"The NEC panel have even accepted that they were wrong to raise questions of my membership of the party, as I have been a full member since 2011.
"They did not identify my payments in the Ukip records until I showed them my own bank statements. After providing evidence of the payments and donations I have made to the party, they were satisfied this was not an issue.
"They have failed to accept that there were serious issues with the application system despite providing evidence that attempts of submission were made before the deadline. The NEC deny this is the fault of the Ukip system.
"Furthermore, highly confidential information about me held in party documents has been leaked to the press and the NEC has not sought to investigate this gross breach of privacy."
Three members of the party's NEC immediately resigned from the committee in protest over what they described as the "deliberate obstruction" of Mr Woolfe's nomination.
Victoria Ayling, Michael McGough and MEP Raymond Finch said the "escalating megalomania" of members of the board had been "detrimental to the functioning of the party".
The NEC "has essentially usurped full governance of the party" and is "collectively in pursuit of oligarchy, self-promotion and cronyism", they said.
