It is thought Burridge, who joined HHCL in May 2001 with a remit to redefine and grow the agency, will take a role within its parent company Chime, although it is unclear what this will be.
Howarth joined the agency in 1996 and was the client services director when he was promoted to managing director in January 2002. The Red Cell chief executive, Lee Daley, is believed to have been impressed with his performance which has included winning and retaining key accounts, such as Go and a place on the Mars roster and running the agency on a daily basis.
A decision on the deal with Red Cell, which would see HHCL become the network's London office, is expected to be finalised next week.
Neither Chime nor HHCL would comment on the story as Campaign went to press.