Mobbs will fulfil the same role at Publicis Dialog, where he will oversee the direct and digital marketing accounts for the companies.
Mobbs began his career at Reader's Digest, before moving to direct marketing agency MSW Rapp & Collins. He also worked at Ogilvy Mather Direct and in 1995 established his own direct marketing agency in South Africa.
He returned to the UK in 2000 to take up a position at Clark McKay and Walpole, before moving to Harrison Troughton Wunderman, where he oversaw the Star Alliance, Vodafone and DHL accounts.
Mobbs said: "I've joined Publicis Dialog because I believe we can achieve even greater things with two of the UK's most powerful brands. The agency has a reputation for developing impressive integrated marketing communications and the opportunity to join such a strong outfit was just too good to miss."
The appointment comes after a period of intense activity at the agency. Last week, UK chief executive Simon Marshall resigned, following global chief executive Colin Hearn's departure, amid extensive changes to the Publicis group's digital offering.
The network is launching a digital brand called Publicis Modem to sit alongside Publics Dialog and the network's other agencies.
Martin Reidy becomes chief executive of Dialog Worldwide, with Publicis Modem based in San Francisco.