Stagg will oversee the management of More2's database and e-marketing clients including The White Company, Smythsons, Molton Brown, Abel & Cole and Charles Twryitt.
She will be responsible for strategy across the client service team as well as developing More2's data service offering with the support of the database analysis and software development teams.
Stagg said: "More2 has an impressive client base and I heard excellent things about their reputation for transforming businesses and consistently delivering results.
"I'm looking forward to bringing my expertise to one of the UK's fastest growing agencies and working with ambitious clients to help devise effective marketing strategies."
Stagg first joined Experian in 2004, having previously worked for NCH Marketing Services where she managed clients including L'Oreal, Garnier and Proctor & Gamble.
Kevin McSpadden, managing director of More2, said: "Anne's experience at Experian heading up major clients across UK mail order, FMCG and financial services, as well as her strong track record in developing strategic client service teams, made her the obvious choice to head up our data services division."