David Evans, MD of Croydon-based The Campaign Company, is providing strategic advice to Benn's campaign.
TCC played down Evans's role, saying he was advising in ‘a personal capacity in his spare time'.
Evans was assistant general-secretary of the party before co-founding TCC five years ago, and is described as ‘an old friend' of Benn's.
Benn's father Tony lost out to Denis Healey in the race for the same role in 1981.
