The publisher of current affairs magazine The Economist has tasked Edelman with raising the profile of the business and increasing its corporate voice in the UK media sector.
The brief is believed to be a new account and Edelman is thought to have won the business via a competitive pitch.
The brief is understood to be focused on group-level comms rather than the promotion of individual titles or consumer-oriented work. It is thought that The Economist Group is looking to create a powerful voice in public and political discussions on the UK media industry, and Edelman's appointment is part of this drive.
Edelman and The Economist Group confirmed the appointment, but declined to elaborate on the brief.
Speed Communications' work on The Economist's editorial side will not be affected.
Nick Barron, deputy MD, corporate and financial, and media director Jo Sheldon will lead the account, reporting to The Economist Group's brand comms manager, UK, Caroline Marrows.
There are several publications under The Economist brand: The Economist online, Economist Intelligence Unit, Economist Conferences, Economist Corporate Network and Intelligent Life.
The group also owns CQ Roll Call and European Voice, aimed at decision-makers in Capitol Hill and Brussels respectively, as well as cash, treasury and risk publication EuroFinance.
It is one of the few media brands that has performed strongly throughout the economic downturn, with group turnover and operating profit growing year on year for the past five years.
In the year to 31 March 2011, group turnover was £347m and operating profit £63m.
The Financial Times owns half of the group, but The Economist retains an independent corporate voice as it is an associate of the newspaper's parent company Pearson, rather than a subsidiary.