Barber, who joined BHWG, which later became Proximity, 16 years ago, has been the director of client services for the past two years. She will now be responsible for the day-to-day running and operational management of the business and will report into Phillips.
Phillips said: "Her inherent understanding of the agency, its clients and its people makes her the perfect candidate to drive the agency's ongoing operational excellence."
Barber said: "I am excited by the opportunity to have an instrumental role in the running of the entire agency."
Proximity's managing partner, Emma Rush, will take on Barber's former role.