Ukip chairman Paul Oakden has stepped down in the latest indication of the chaos within the party.
His final act in the role will be to chair an extraordinary general meeting of the party to decide on the fate of embattled leader Henry Bolton on Saturday.
Mr Oakden said his decision to quit was made "irrespective of the outcome" of the meeting, which is expected to attract thousands of Ukip members.
Party officials denied Mr Oakden's departure was related to an email gaffe over the weekend in which he signed a message to party members "interim leader".
In a message announcing his resignation, Mr Oakden said he had voluntarily terminated his contract at the end of January and had now decided that his role would end after the crunch EGM in Birmingham.
Mr Oakden said: "I have made this decision irrespective of the outcome of the EGM and I'm announcing it now to ensure that it remains absolutely unconnected to whatever democratic decision the membership may take on Saturday.
"As party chairman, appointed by the leader but answerable to the NEC, I have been required to remain impartial in the current process.
"As always, I have absolute faith in our membership to do what is necessary to protect the long term future of our party."
Mr Bolton is clinging on to the leadership despite a revolt by several senior figures in the party in protest at his relationship with model Jo Marney.
Mr Bolton has admitted he still has "strong affections" for his former girlfriend who sent racist messages about Meghan Markle.
The party's ruling national executive committee backed a motion of no confidence in Mr Bolton last month after it was revealed 25-year-old Ms Marney had made highly offensive comments about Prince Harry's fiancee and black people.
He now faces a vote over his leadership at the special meeting of party members.
Additional reporting from the Press Association.