He is to leave the agency in April after a stint that has seen him set up the company's brand planning division and heading new-business pitches that led to winning a place on the COI strategic planning roster, Adidas's media planning account and the Eagle Star business.
Regan was also part of the team that secured the TV Licensing account in a joint pitch with other AMV Group companies.
Regan, a founder of media strategy agency Michaelides & Bednash, joined PHD in January 2001 as the agency's first brand strategy director, sitting alongside managing director Morag Blazey.
He started his career in market research, before moving to Cogent in an account planning role. He then helped to found Bullet Media, HHCL & Partners' joint venture with The Media Business, and was named by ±±¾©Èü³µpk10 magazine in its list of top 10 media planners for 2001.
According to Regan: "Over the past few months I've been getting restless for my next challenge, and seeing lots of exciting evidence of change in the industry as a whole. I'm having talks with various people, and I've decided to take some time away from work to explore them further."
PHD has not yet revealed succession plans following Regan's departure.
PHD chairman Jonathan Durden said: "We have enjoyed Tony's contribution to our company and our time together. He is a great human being, and has helped us develop our brand planning skills. We will miss him and wish him a very happy future."
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .