The appointment will mark the first time the UK Government's buying business for all its departmental advertising campaigns has been consolidated into one group and ends a six month review process.
The WPP consortium, made up of specialists from MediaCom, Mindshare and Mediaedge:cia, fought off strong competition from a Starcom and i-level alliance called Smile, and an Aegis offering called Unify.
M4C's successful team was led by GroupM's chief operating officer Nick Theakstone, MediaCom's UK chief executive Jane Ratcliffe and MEC's deputy managing director Alex Altman – who is expected to take a lead role in the new set-up.
Theakstone admitted he was "absolutely delighted" with the win and said the pitch process had brought out the best of WPP's collaborative arm.
"The COI pitch has seen GroupM at its best," he said. "We were able to draw on all the very best specialist knowledge the industry has to offer to create a bespoke offering that will be able to service all of the COI's many different needs."
The pitch follows rapid changes in the media landscape led by digital technologies.
The COI’s most recent annual report shows that government departments and public sector bodies spent a total of £211m on media and £40m on online advertising during 2008/9.
The new framework has been established to enable full integration and is expected to deliver a number of benefits for the COI and its public sector clients, including increased efficiencies both within and across channels.
Digital is expected to play an increasingly large role in COI’s communications in 2010 and beyond, as government departments look to increase dialogue with target audiences while managing expected cuts in marketing budgets.
Peter Buchanan, deputy chief executive of COI, confirmed the decision and said: "This has been the largest competition of its kind ever to take place in the UK. The responsibility to come up with the right decision has been considerable and I am indebted to the judging panel for their expert advice and wisdom.
"I am confident that we have a visionary, integrated buying approach, which will enable us to face the media market challenges, going forward."
To-date, COI's media buying business has been separated by medium and currently has six media buying contracts with Aegis's Carat handling the buying for TV and cinema, MediaCom the press, i-Level controlling digital, Starcom the radio and Aegis' Posterscope responsible for outdoor.