Agencies chosen to be part of the group include Berlin Cameron/Red Cell, HHCL/Red Cell, the recent Spanish addition to the network, Sra. Rushmore/Red Cell, and the Argentinian shop WM/Red Cell. They will drop their Red Cell branding in favour of the new name United.
The network's Paris office, Les Ouvriers/Red Cell, and the network's outposts in the Nordics and Australia are also linked with the venture.
"There will be no closures," Berlin said, commenting on speculation in the US press that the remaining agencies were facing an uncertain future.
He did not, however, dismiss the possibility of further mergers of Red Cell shops with other WPP agencies around the world.