A Conservative councillor and parliamentary candidate in Hull has defected to join UKIP, the party said on Monday.
Michael Whitehead, an East Riding councillor, is standing in the general election against former Labour home secretary Alan Johnston.
UKIP said in a statement that Whitehead was "disgusted" with the ruling Tory group in East Yorkshire and with Conservative party HQ for failing to stop its "secretive" behaviour.
Whitehead said he had been concerned about the behaviour of leading Tories in the area since 2011, and that he wanted to "open this secretive council up and make it more transparent and work better for the residents rather than to the benefit of the few".
UKIP leader Nigel Farage said the move showed UKIP was "the real party of opposition to Labour in the north".
Whitehead's chances of winning Hull and West Hessle are slim in any case: Johnson is defending a majority of 5,700 in the constituency.
However the Conservatives were quick to say that Whitehead was in fact "sacked" by the party last week, adding that his appointment by UKIP was "cynical".
Statement on Mike Whitehead, sacked last week
The Press Association has obtained a letter sent to Whitehead on Friday from Conservative party HQ informing him that the party was "refusing" to nominate him as a candidate. It said:
As you have stated that you intend to stand in the local election, despite not having been selected for the party, and despite Mrs Clarke asking you to agree to support whoever is properly selected by the association to fight the Willerby and Kirkella ward, I am forced to act to protect the party by refusing to agree to you being nominated to represent the Conservative party at the 2015 general election as candidate for Hull West and Hessle.
The shadow cabinet officer minister, Labour's Jon Trickett, said the move was a blow to the prime minister's authority. He said:
This is another huge blow for David Cameron's authority. Even his candidates know he cannot win a majority.
UKIP and the Tories increasingly share the same people as well as the same policies. Both stand for increased health service privatisation, extreme spending plans which threaten the NHS and further tax breaks for those at the top.