Their decision to leave follows the changes in April to the agency's creative department, which saw Paul Brazier replace Peter Souter as the executive creative director.
Belford and Roberts maintain they are both looking for a new challenge outside AMV. Roberts said: "We've had a good time in the past 12 months. It is a shame to be leaving the agency but we wish everyone at AMV all the best for the future."
Farah Ramzan Golant, the chief executive of AMV, said: "With a new leader comes the opportunity to change the way we look at the structure of the department. We have no plans to replace the pair or do any recruiting that follows the old AMV model. We're not looking to give out titles, but want to get creatives working on projects."
The pair, who were promoted to joint creative directors in March 2004, are holding discussions with agencies about new roles but were unable to supply specific details.
Before joining AMV in 2002, the duo worked at Ogilvy & Mather. While there, they were embroiled in a controversy surrounding doctored ads entered for the Campaign Press Awards.
The pair were lured to O&M from TBWA\London in 2001.
While at AMV, the pair were responsible for recruiting several new teams to the agency as well as contributing on new-business wins. Ramzan Golant said: "They have also won a number of gold awards this year, including The One Show and a Cannes gold."
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