A former RAF pilot tasked with making Ukip look more professional has stood down as chief executive "by mutual agreement" after just eight months in the job.
A party spokesman said Will Gilpin's rolling contract would not be continued.
Mr Gilpin was appointed in December last year to make the party sound and look more professional.
Party sources said that Mr Gilpin was hoping to return to corporate IT, the sector he left back in December, which they said "he is far better suited to".
According to the BBC the party suggested that Mr Gilpin had struggled to adapt to working at a smaller organisation whose "DNA is individualistic".
Mr Gilpin is said to have left on good terms.
A Ukip spokesman told the BBC: "We thank him for his time, effort and the hard work he has put in and wish him all the best for the future."
After his appointment last year, Mr Gilpin had told the BBC his job was to "deal with the inertia of a party that is used to doing things in a very relaxed, very uncoordinated manner".
It is not yet known who will replace him.