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.
Diane James wrote "under duress" in Latin on her registration forms when taking over as leader, Ukip's Lisa Duffy has claimed.
The leadership candidate, backed by many in the anti-Farage wing of the party, said: "My understanding is that is what's happened, but I haven't got proof myself."
The former party director, who said she would not rule herself from running in another leadership election, said she was not surprised that James stood down so quickly, after offering no leadership over the past three weeks.
Speaking to BBC Radio 4's Today programme, Duffy said: "I didn't believe this was something that she particularly wanted to do or had the passion to do. So I'm not surprised."
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.