Abbott Mead Vickers BBDO broke through the half-a-billion-pound billings barrier for the first time in 2015.
Billings grew by 8.4 per cent year on year to £511 million for the Omnicom agency, which has major spenders such as Sainsbury’s, Camelot, Mars and Currys PC World on its books.
Ian Pearman, the chief executive of AMV, said: "This reflects the consistency of its clients as much as the agency."
He added: "Creative and effectiveness awards is a much more important metric."
The table supplied to Campaign by Nielsen also shows that Grey London has entered the top ten for the first time, climbing six places to number eight.
Grey’s billings increased by a whopping 37.2 per cent to £203 million as it won 14 new accounts last year, including the £53 million Vodafone UK business.
Nils Leonard, the chairman and chief creative officer at Grey London, put the success down to working with "influential and ambitious" clients.
But it was not all positive news. Rainey Kelly Campbell Roalfe/Y&R, which had a rough 2015 with the loss of Jaguar Land Rover and Lloyds Bank, saw billings plummet 19.1 per cent to £189 million.
M&C Saatchi, which fell out of the top ten for the first time in 2014, dropped out of the top 20 last year. Billings declined 28 per cent to £87 million.
CHI & Partners dropped to 16th place, while Wieden & Kennedy’s Tesco loss meant that billings decreased by 36.6 per cent.