Talking on camera for the first time since WPP shareholders delivered one of the biggest investor rebukes to executive pay in UK corporate history on 13 June, Sorrell criticised the current standards being applied by ISS, which advises around 20% of WPP investors.
Reminding that WPP achieved "record profits" in 2011, with pre-tax profits up 18.5% to £1.008bn and revenues topping £10bn, he said he was "very proud" of the performance.
Despite the group’s financial results, which continues to be propelled by an aggressive acquisition strategy, the value of WPP’s shares have fallen 15% in the year.
Sorrell said: "The performance statistics against our competition are very strong, we either lead or are second in pretty much any period that you care to take."
Turning on the metrics used by ISS to advise investors, which views WPP as a UK company and not against Omnicom, IPG or Publicis, the 67-year-old leader added: "I don’t mind these standards being applied as long as they are applied consistently… All of our executives on the board would look underpaid in relation to those three companies [Omnicom, Publicis and IPG].
"The ISS says that we’re not a global company, that the comparisons are not global comparisons, and I totally disagree with that."
He added as a parting shot to WPP’s closest rival: "Nobody mentions that the chairman of Omnicom [Bruce Crawford] is the former CEO, I think he’s 82 or 83, I think he’s been on the board for 25 or 35 years, and I think I’m right in saying that every member of the board of Omnicom is over 60 and has been on that board for 10 or 15 years."