A former director-general of the Advertising Standards Authority, Alderson replaces John Bridgeman, who has stepped down after completing his second term in the role.
Alderson is the managing director of FireHorses, which provides advice on regulatory policy and strategy to clients in the public and private sectors. She is also an active press complaints commissioner.
Alderson, who co-founded the European Advertising Standards Alliance in Brussels in 1991, spent nine years as the secretary to the Committee of Advertising Practice. She also took on the role of director-general at the ASA between 1999 and 2000.
Alderson said: "Over the next few months, I'll be tasking the Authority with a review of its working practices to ensure they're comprehensive and responsive to new developments in this dynamic industry, and will be asking the industry to work with the Authority in improving its profile with the public and practitioners."