Ukip MEP Bill Etheridge said he was "very disappointed" party leader Diane James has quit in just 18 days adding that her reasons given were "pretty unclear".
The West Midlands MEP, who stood against James in the leadership contest, told ITV's Good Morning Britain that the statement she made was "rather peculiar".
In a statement released on Tuesday, James said that it had become clear in discussions with party officials she did not have "sufficient authority" to push through changes she had planned.
Speaking from Strasbourg, Etheridge said: "That's rather a peculiar statement that she's made because, as far as I'm aware, being out here in MEP's meetings and mixing with colleagues. We've all been here ready and willing to help and support Diane in what she wanted to do."
He added: "I stood against her on a different platform, I don't agree with everything she said but I can certainly say I was waiting for the call.
"She won the election fair and square and we were all ready to back her."
But Etheridge, who said he would not rule out standing again for leader, added he "wished her well" and described her as a "good MEP".