Raheem Kassam has hit out against claims by rival Ukip leadership candidate Suzanne Evans that he wants to take the party in a far-right direction.
Mr Kassam, whose leadership bid was endorsed by Ukip's highest profile donor Arron Banks, told ITV News that Ms Evans was "talking nonsense", and insisted that he has never considered himself to be far right.
"I was really disappointed that 60 seconds into her campaign being launched, she goes to personal and negative attacks on somebody else in the party," he said.
"I don't think this should be about that, this should be about policies," Mr Kassam added.
He insisted that Ukip has been labelled far-right by the "Remain campaign and the project fear types", and accused Ms Evans of "co-opting their messaging".
Mr Kassam, a former aide to Nigel Farage, said he was ready to be the "CEO of Ukip", and outlined his policy beliefs, including taking the lowest paid out of the tax system, and making it simpler; lowering immigration after Britain leaves the EU; and ensuring that a "proper, hard Brexit" happens.
Announcing her leadership on the BBC's Andrew Marr Show on Sunday, Ms Evans said Ukip had developed a "toxic" image after being cast as a far-right party - something she said would continue if Mr Kassam was elected leader.
Speaking on ITV's Peston on Sunday, Nigel Farage criticised Ms Evans's comments and said he would not be supporting her leadership bid.
A fresh Ukip leadership race was prompted after Diane James resigned after just 18 days into the job.