Speaking at the Mobile World Congress in Barcelona yesterday, Sorrell said the app market has tripled in size to $15bn, but that was small "if you remember our industry is about a trillion dollar industry".
Asked how the ad industry can make the most of the boom in apps, he replied: "I think the real answer is with difficulty because it's not dissimilar to what you're seeing with newspaper and periodicals because the amounts of income here and the revenues generated is becoming more significant but is highly fragmented.
"You have a vast array of applications and a vast array of designs and consumer loyalty is quite fickle ... It's very volatile."
Sorrell believes the biggest opportunity is in faster growth markets such as China where there are 700-750 million people have got mobiles.
"It's going to become a very powerful, not just advertising medium, but a very powerful way for people to buy things ... we'll largely become a cashless society over time."
He also covered how WPP is addressing the mobile market and social networks, saying that Facebook's latest valuation of $60bn was "frothy".
This footage is made available to Campaign by CNBC