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.
'Elephant in the room'
Auletta and Sorrell arrived on stage to cheers from an audience of hundreds, for a talk that was described as one of the most "anticipated" sessions of the week. Later in the discussion, Autella turned the tables to ask Sorrell about the "elephant in the room", referring to the events of the past six weeks.
When asked about the accusations in a Financial Times investigation that Sorrell was "cruel" to staff at WPP, he responded: "Am I an easy person to deal with? No. Am I demanding? Yes. I don't think that was fair. I think I demanded high standards."
Auletta asked Sorrell why he had kept quiet throughout the claims, but the ad boss refuted this by saying that there were formal responses to each and every accusation.
When pushed further about claims that he had used company funds for prostitutes, Sorrell replied: "That’s been dealt with too, and it was strenuously denied."
"So why not speak to that?" Auletta responded.
Sorrell explained: "We dealt with that by strenuously denying it." Only when Auletta asked whether it was true did Sorrell reply: "It’s not true."
Sorrell reminded Auletta that the FT article explained that there was an investigation but this did not find anything. So Autella asked why he left if this was the case.
"I found the situation had become untenable and was in the best interest for the share owners, the clients and people inside the company," he said.
Later Auletta asked whether there will be a point at which Sorrell will "open up even more", to which he responded: "We'll see how events develop."
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.