He is set to leave his role as managing director, EMEA and London, at Ogilvy later this year, after six years with the agency.
Coleman-Smith will join Berwin Leighton Paisner as director of marketing and a board director. He will lead a marketing team of 25. As part of a strengthened board team, he will also support the firm's ambitious growth strategy.
Coleman-Smith joined Ogilvy in 2004 and is a board director within Ogilvy Group. He will not be directly replaced in his UK MD role and Ogilvy will assess whether it needs to hire an EMEA head.
Coleman-Smith has spent more than 22 years in the PR industry. Before joining Ogilvy, he worked at agencies including Cohn & Wolfe, Edelman and Hill & Knowlton.
He said: 'Being on the board of Ogilvy and working on 360 campaigns has given me the experience and taste for a wider marketing role. I wanted to join an organisation that was ambitious and where there was a chance to make a real impact.'