Pigsback, which has more than 350,000 registered UK users, said Harrison would help manage private investor firm Hotbed's 拢2.5m October investment in the company, as it aims to take its membership to 1m by the end of next year.
Harrison joined Thomson in February 2005 when he was appointed to the role of general manager at Thomson Directories' internet development group. He was responsible for growing sales across of all Thomson's internet services, including products such as and search engine marketing service .
He joined Thomson from the Institute of City & Guilds, where he was senior commercial manager for e-strategy and learning.
Michael Dwyer, chief executive officer at Pigsback, said: "Brian's strong search marketing background will be invaluable as we develop long-term relationships with our members and continue to generate strong revenue for our brand partners.
"Brian will be building upon this expertise to facilitate open, measurable relationships between brands and our members."
The company, which launched in the UK less than 12 months ago, claims to be the sixth most-visited website in Ireland.
Harrison said: "We have numerous initiatives planned over the coming months to accelerate this growth."
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .