He will be tasked with developing the commercial function of Fairtrade in the UK through the next stage of growth that has seen retail sales rise from £16m in 1998 to £800m in 2010.
He will liaise with Fairtrade-certified companies from the UK headquarters in London from later this month, heading up the 20-strong commercial team.
"I am thrilled to be joining the Fairtrade Foundation at what is a hugely exciting time for the Fairtrade movement in this country," said Deo. "My role will be to deepen and extend our relationships with our existing partners and to help achieve growing sales of Fairtrade products."
Prior to joining the Foundation, Deo had spent 12 years at Diageo. Since 2006 he was the group's commercial development director for global procurement, and before that he held a number of key roles, including strategy director for its Asia markets and strategy director for global supply.
The 46-year-old started off his career in 1987 in his native India as a brand director for P&G's health and beauty portfolio.
Deo's wealth of experience in global roles would be an asset to the Fairtrade movement, said executive director Harriet Lamb.
"Ashish has enjoyed a successful career with a string of notable achievements," added Lamb. "He is the ideal man to take Fairtrade to the next level and we are delighted to have him on board."