Steven Woolfe has hit out at Ukip's ruling committee after it voted to exclude him from the party's leadership contest.
In a statement following the verdict, Woolfe said that Ukip's National Executive Committee "is not fit for purpose", and three NEC members have resigned in protest.
“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," Woolfe said.
“If I were on the ballot, I would have fought to reform the internal structure of Ukip including the NEC. Ukip must professionalise and it cannot do that with an unfit NEC," he added.
A spokesman for Woolfe said he "is considering all options" in response to the verdict, meaning a legal challenge could be forthcoming.
It comes as three members of Ukip's ruling committee have quit in protest at the decision.
While the party said that "a clear majority" of the NEC backed the decision, Victoria Ayling, Raymond Finch and Michael McGough have all called for a vote of no confidence in the ruling committee.
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The trio accused the ruling body of "deliberately obstructing" Woolfe and accused some of its members of putting personal ambitions ahead of the interests of the party.
"Steven Woolfe is a popular candidate among Ukip's members and should be permitted to represent those that wish to vote for him," they wrote.
"To purposefully trawl for technicalities upon which to base a decision to deny his inclusion is not in the best interests of the membership and truly injurious to Ukip."