Diane James has quit as leader of Ukip after just 18 days in charge.
The 56-year-old said it had become clear in discussions with party officials that she did not have "sufficient authority" to push through changes which she had planned.
Steven Woolfe has become the first leadership contender to throw his hat in the ring following the shock resignation of Diane James.
Mr Woolfe was barred from standing in the last leadership contest after submitting his nomination papers 17 minutes late.
His announcement came as Nigel Farage confirmed he would be carrying on as interim leader until a permanent successor was in place - prompting a furious row within the party.
Diane James has quit as Ukip leader before most people knew who she was. What happened?
Bill Etheridge, who stood against Diane James for leadership, said he was disappointed at her resignation adding she was supported by MEPs.
She has been in the role less than three weeks.