It is the second time the issue has been raised in recent months. In the summer, a leading shareholder group attacked the ad giant for its lack of a succession plan.
The shareholder activist group RREV, run by National Association of Pension Funds and the US corporate governance organisation body ISS, said there was no hint who would succeed Sorrell.
According to a report in the Sunday Times, two independent board directors see lack of a visible succession and issues of Sorrell's management style as issues at WPP.
The two, Christopher Mackenzie, formerly of GE, and Paul Spencer, formerly of Royal & Sun Alliance, want the WPP chief to provide more details to the board on major financial deals.
The recent aborted deal to take over Aegis in partnership with US private equity firm Hellman & Friedman caused problems about the lack of information provided to board members.
The paper quoted one board member as saying that the two felt that they were not quite in the loop on everything that was going on and wanted to be provided with more detailed financial information.
The lack of any perceptible successor to Sorrell, who will be 61 this year, is also said to be an issue. Sorrell has led the UK advertising group for more than 20 years.
However despite the tensions, Sorrell, who has built WPP into the second-biggest marketing services firm in the world with than 84,000 staff, still has the full support of his board.
Philip Lader, WPP chairman, told the paper: "I don't deny that there may be some who want more or less of something, but that is healthy for a board.
"There may have been one director or two that may have preferred more detailed information at various points."
Lader added that WPP reviewed the succession every year, but has a policy of not publicly disclosing individuals or lists of candidates, which the chairman said was a policy that he supported.
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