The threat by Tony Leyshon could ensure that the Tory MP Jacques Arnold, who is defending a majority of 5,000, holds on to the marginal seat of Gravesham in Kent.
Dr Leyshon, a local orthopaedic surgeon and Labour Party branch secretary, was barred from selection as the Labour candidate for Gravesham at the weekend because he had not been a party member for two years.
Last week, Labour's National Executive waived the two-year rule in Mr Howarth's case on grounds of "exceptional circumstances", because he was already an MP and a member of the Parliamentary Labour Party. He was declared eligible to put himself forward as a Labour candidate.
Dr Leyshon told the Independent yesterday: "Yes, I am worried that this might hand the seat to Jacques Arnold, but it is important that the Labour Party is seen to be a truly social democratic party. You've either got a rule book or you haven't, and it doesn't seem very democratic to apply it differently for someone else."
Dr Leyshon, who joined the Labour Party two years and three days ago, had not been a member long enough to qualify at the start of the Gravesham selection process. He resigned last night as a branch secretary in Meopham and Cobham, and from the party. His branch chairman, Michael Finn, also resigned in protest, saying Dr Leyshon had been "ill-treated".
The Gravesham Labour Party on Sunday chose Chris Pond, long-serving director of the Low Pay Unit and husband of the Labour Euro-MP Carole Tongue, as its candidate for the general election.Reuse content