UKIP could face a court challenge after its high command rejected demands for a vote on whether to hold a leadership contest.
Fifty-one branch chairmen who support MEP Robert Kilroy-Silk have called for an emergency general meeting - enough to force the move under party rules.
But the leadership says the motion is invalid as the chairmen need to hold local meetings to support the demands.
The emergency general meeting would vote on whether to hold a postal ballot of party members on choosing a new leader. However, Roger Knapman says that his telephone poll shows he has the support of the party chairs. Kilroy-Silk declared the poll as unfair.
UKIP spokesperson Quentin Williamson said: "The faction which wants to press Robert Kilroy-Silk forward as potential leader has gathered the signatures of 51 branch chairmen to demand an emergency general meeting of the whole party.
"It was presented to the national executive committee on Monday. But to have an emergency meeting it means all those branches must have had an emergency general meeting to permit their chairman to do so.
"This has not happened in any case."
London Assembly member, Damian Hockney will meet with lawyers next week to discuss the next step for the party. He said: "We have to take advice immediately because because if we are going to do something, it has to be done quickly so it does not conflict with the election campaign."
And he said the leadership was concentrating on campaigning efforts, with its first election "campaign shop" due to open on Wednesday in the target seat of Thanet South.
Ex-chat show host Mr Kilroy-Silk says UKIP would self-destruct if the leadership expelled him from the party.