Wallinger joined HS&P a year ago to help set up data.HS&P, the agency's branded data offering, following a 10-year career at Craik Jones.
As data planning director at Craik Jones, Wallinger helped develop new business at the agency with Unilever, Boots, COI, Diageo and Orange.
He began his career at Rank Xerox, and also held roles at O&M Direct, BMP and Aspen Direct.
HS&P confirmed that Wallinger has left the business saying that he stepped back to pursue other options.
Data.HS&P will now be headed up by planning director Dan Thwaites and will continue to offer data expertise. HS&P saiid clients could buy advice on data as a standalone offering, or in coordination with the agency's relationship marketing hub, and specialist divisions in loyalty and word-of-mouth, The Loyalty Practice and Legends.
Mark Runacus, chief strategy officer at HS&P, said: "John has been instrumental in the successful launch of data.HS&P and we want to thank him for his commitment and support.
"Data.HS&P is an established, profitable division of the business, and that is in part, down to the experience and energy John and his team brought to the launch. We wish John all the best for future endeavours."
Wallinger said that he had been "thinking about the future" and decided to "pursue a business idea" that he had been thinking about for some time. In the meantime he is doing freelance work for clients.
He said: "It's been fantastic to be involved with an agency going through such a period of innovation. It gives me a great deal of satisfaction to see data.HS&P operating as we had always intended, and now I feel it is time to consider the other options available."
Earlier this month it emerged that HS&P is set to sign a deal to merge with digital agency Crayon to provide its clients with a wider digital offering.