James Clark, who was director of news and press secretary to the secretary of state at the Ministry of Defence from 2002 to 2007, has joined the City agency as it looks to expand its offering.
Clark told PRWeek: 'The group has come through the global financial crisis extremely well and is now on an expansion curve.'
The agency will look to tap into Clark's experience of advising in both the public and private sectors, crisis management and political understanding.
Clark joins after the recent news that Cardew MD Rupert Pittman is to leave to become comms chief of British defence contractor Chemring Group. Pittman will become Chemring's director of group comms and investor relations from 15 September.
Most recently Clark has worked as a freelance comms consultant, having headed comms, marketing and public affairs at Oxfordshire County Council and been a director of comms and government relations at management consulting firm Bearing Point.
He has also worked as a journalist for the Sunday Times and the Daily Mail.