Campbell has axed eight jobs in total, four of which are group creative heads: Paul Diver, Alan Morrice, Jack Stephens and Rob Neilsen.
Campbell has also confirmed the appointment of Petrina Kilby as the head of TV. Kilby took over as the acting head of TV when Sarah Martin left last July.
Frank Leiberman, who was enticed out of retirement in March to run the agency's TV department on a temporary basis, is to become the permanent executive head of TV.
The agency's creative direction is being split between Campbell, Luke White, Marc Bennett and John Hurst, who has also taken on the role of global creative director on Nescafe.
These are the first redundancies Campbell has made since he joined the agency in January.
The changes are part of an overhaul of the agency aimed at improving its creative product to prevent further client losses and help improve its new-business performance.
In the past six months, the agency has lost accounts including Norwich Union, Greene King and Birds Eye.
The job losses come during an unsettling period at the agency following a number of senior management changes.
This week, Stephen Whyte, a former head of client services at McCann in Europe, took on the role of chief executive.