Tony Benn's son will represent Labour in the by-election on 10 June, called following the death of Foreign Office minister Derek Fatchett.
Mr Benn Jnr, a special adviser to Education Secretary David Blunkett, beat four others on the short-list for the safe seat. Mr Fatchett had a majority of over 20,000.
Mr Benn, 45, a Labour party member from 16, previously worked for the union, MSF; and Unions 21, the trade unions think-tank and as an Ealing, London, councillor.
His father is a leading critic of Nato's military action against Yugoslavia, is a former Cabinet Minister and contender for the party leadership during the 1980s. He has served as an MP since 1950, and MP for Chesterfield since 1984. Tony Benn denounced his hereditary title of Viscount Stansgate during the 1960s to be able to continue to sit in the Commons after he inherited the peerage.
Tony Benn said his son would be an "excellent" MP. "He's his own man, he's very very hard-working, very well respected," he said. "It was quite an achievement to be selected in Leeds because he hasn't got any local links."
Mr Benn said he hoped to be able to introduce his son to Parliament.