Peter Kilfoyle

Yesterday, Ms Berger declined to respond to Mr Kilfoyle’s attack, but Peter Dowling, the constituency party secretary, insisted she was simply the most impressive candidate.

Mr Dowling, who is Ms Kennedy’s partner, said: “Those members who met Luciana – and I’m not sure Peter has – were impressed by her experience and local knowledge.”

Asked about the LFI connection, he added: “Jane gave Luciana her backing because they worked closely together and she knows her abilities – it had nothing to do with that particular organisation.”

Ms Berger, who has worked for a management consultancy and the NHS, is believed to have defeated Ms Simon by a margin of 94 votes to 50, having mounted an energetic door-to-door campaign, signing up many students.

The vacancy was created by Ms Kennedy’s decision to stand down after 18 years, describing an MP’s life as “draining and exhausting”.

Relations were also strained between Mr Kilfoyle and Ms Kennedy, who accused the leftwinger of “treating his constituents with contempt” in his bid to topple Tony Blair.