The Omnicom network posted more than double the score of the second-placed MindShare after clients including McDonald's and Nissan won at several major awards festivals in 2007.
In addition, two of its campaigns, "money goes digital" for the ASB Bank in New Zealand, and its Doritos "crash the Super Bowl" activity for Frito Lay in the US, won major media awards at Cannes.
Starcom MediaVest, the second-most-awarded agency in 2006, slipped to fifth place, while Universal McCann rose one place to fourth. OMD's sister creative network BBDO shot from 14th to third after its "Barrio Bonito" work for Nike through BBDO Argentina won major media awards at festivals including Cannes.
Nike was named the advertiser of the year for the second year running after winning awards at 18 different festi-vals for the football-themed activity, which featured players including Ronaldinho.
The report, sponsored by Procter & Gamble, showed that the "Barrio Bonito" campaign was the most-awarded single campaign, ahead of activity for Nissan Qashqai in second place.
The US emerged as the most-awarded country with 185 points, just ahead of the UK on 167 points.
However, the US score was down 4.3 per cent on 2006. Germany and Spain were the third- and fourth-ranked markets.
Omnicom Media Group was the most-awarded holding company group, with Group M in second place and Publicis Groupe Media in third. Interpublic finished ahead of Aegis and Havas in fourth place.
Daryl Simm, the chairman and chief executive of Omnicom Media Group Worldwide and the acting chief executive of OMD Worldwide, said: "It's extremely satisfying that OMD is the Gunn Report's agency of the year for the fourth year running.
"I am also pleased that Omnicom Media Group has scooped top spot for global media agency network, too.
"Both accolades are a wonderful tribute to all our people around the world - in OMD and across OMG - and to their skill, desire and determination for creating outstanding media ideas that deliver real results for our clients."
Top agencies 2007
Rank Agency Points
1 OMD 234
2 MindShare 110
3 BBDO 101
4 Universal McCann 87
5 Starcom MediaVest 81
6= Carat 57
6= MediaCom 57
Top clients 2007
Rank Advertiser Number of Points
1 Nike 18 58
2 Coca-Cola 16 48
3 McDonald's 12 31
4 Adidas 9 30
5 = Axe 9 20
5 = Nissan 5 20
Source: Gunn Report