Bowles and the founding partner Debbie Klein will take over the day-to-day running of the agency, enabling Stephen Woodford, the agency's chief executive, to focus on developing the WCRS Group.
Julian Hough, the agency's previous business development director, is currently working on secondment for the agency's 3 client.
The restructure also sees the six lead shareholders, Woodford, Robin Wight, Klein, Leon Jaume, Hough and Peter Scott, become founding partners.
Bowles will also become a shareholder, taking a personal stake. He is due to join WCRS in September.
Bowles has spent the past ten years at Lowe. He was promoted to the role of managing director in 2001 but quit the agency in May.
Woodford said: "We have ambitious plans for the WCRS Group and we are beginning to build real momentum in all the agencies.
"Top talent is what will drive growth and I'm delighted Jeremy is joining our partnership. He's arguably the best account man in London in terms of his creative track record and with Debbie, Leon and Leslie (Ali) will make a formidable team.
"Moving away from a conventional management hierarchy will allow us to be more entrepreneurial and creative, focusing on the only things that matter - our clients, our work and our people."
Bowles added: "It is a unique opportunity to join a 25-year-old 're-start up' and to get to work with such a respected and well-liked group of ad people was an opportunity too good to miss."