M&B joins Trident's existing agencies, Starcom, JWT, RPM and AKQA and will now develop new communications ideas for the Trident brand, which launched to widespread controversy in January this year.
M&B's appointment follows months of speculation that the confectionery brand is planning to review its media out of Starcom.
John Phillipson, head of marketing for gum and pocket candy at Cadbury, said the appointment would not affect its existing relationship with Starcom, which will continue to plan and buy media for Trident. "We are not seeking to replace Starcom. They did a brilliant job on the launch," he said.
Trident was forced to rethink its advertising strategy in April, when the Advertising Standards Authority banned its TV ads after hundreds of complaints that the ads were racist.