He will be replaced by Helen Cowlin, chief finance officer of Europe’s largest golf retailer American Golf, and previous to that CFO for clothes retailer Fat Face.
She has also been involved with refinancing and acquisitions.
Houlton will remain with ISG through the reporting of the half year results to facilitate an orderly handover before leaving in June.
Cowlin, 49, brings extensive experience across several industries and strong operational knowledge of multi-country businesses gained from roles at Fritolay EMEA (PepsiCo) as operations planning director and Novartis Medical Nutrition as head of business planning.
Roy Dantzic, ISG chairman, said: “Helen is a proven CFO with considerable operating experience of international businesses in growing markets.
“She brings to ISG a strong track record in financial management.”