Ukip will hold a leadership election after its leader Gerard Batten stepped down on Sunday.
The new leader will be the party's seventh in just under three years.
Ukip chairman Kirstan Herriot said: "We are incredibly grateful to Gerard for his dedicated service to the party and expect to be announcing our new leader in early August."
Mr Batten has been in post since April 14 2018 when he was elected unopposed following the resignation of former leader Henry Bolton.
Ukip lost all of its seats in the recent European Parliament elections in contrast to the Brexit Party, led by former Ukip leader Nigel Farage, which came first in the recent poll, gaining 29 seats.
In the 2014 EU elections Ukip came first, picking up 24 MEPs.
Ukip deputy leader Mike Hookem last month quit his role and announced he will run for party leader.
He said he could no longer support the direction of the party under Mr Batten's leadership.
He added: "Mr Batten's policy direction and associations have given the mainstream media the ammunition to label our party 'extreme' and 'far-right', accusations I do not believe to be true."
Mr Batten has been Ukip leader for 16 months and appointed former English Defence League leader Tommy Robinson as his political adviser in November 2018.
The proposed date for the results to be declared is August 10.
Reporting by Press Association.
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