The former WPP boss, who left abruptly in April, explained that all the holding companies are moving in the same direction – to become more integrated and added that the only difference is the speed in which they are moving.
Speaking during a press conference in Cannes today, Sorrell said that his main regret is that he didn’t do more at WPP.
"When I say more, it’s more of that simplification of the verticals, more client-orientated work, more country management and last but not least the digital underpinning to it," Sorrell said.
"So I would say acceleration of that strategy, which I think by and large is pretty much what everyone else is doing, and as I say it’s not a question about where you’re going, the question is the speed."
He also explained that it is not easy "flip the switch" from a business model that is very vertical to one that is client-orientated.
However, Sorrell went further today during an earlier stage appearance at Cannes, in which he claimed horizontality has been "obliterated" since his departure.
Sorrell, who has already set up a new company called S4 Capital, was interviewing the media writer Ken Auletta about his new book on the industry, Frenemies, which was reviewed earlier this month by Campaign's global head of media Gideon Spanier.
Meanwhile, Quarta, who is leading the search for Sorrell’s replacement, was also in Cannes for this week's festival, as was Mark Read, WPP's joint chief operating officer and interim boss.
Quarta hinted to WPP shareholders at last week’s annual general meeting that the new chief executive is likely to come from the advertising and marketing world.