Rupert Murdoch is facing a fresh wave of pressure from influential investment firms which have clubbed together to challenge his dual role as chairman and chief executive of News Corporation.
Britain's Local Authority Pension Fund Forum (LAPFF) and US-based Christian Brothers Investment Services have tabled a resolution demanding that News Corp appoint an independent chairman in the wake of the phone-hacking scandal.
The shareholder advisory groups Hermes Equity Ownership Services and Glass Lewis have also swung their support behind the resolution ahead of News Corp's annual meeting on 16 October in Los Angeles.
Mr Murdoch has made a raft of changes at News Corp, including a move to split the faster-growing television and movie business from the publishing arm, and he has also ordered tighter rules on internal compliance.
But the 81-year-old media mogul has also courted controversy with plans to give his son, deputy chief operating officer James Murdoch, a bigger role in charge of Fox's TV networks in America, despite the UK media regulator, Ofcom, criticising his handling of the hacking scandal.
Ian Greenwood, the LAPFF's chairman, said: "Whilst we recognise the efforts the company has made to clear up the mess left by the hacking scandal, we continue to believe that News Corp and its shareholders would benefit from the appointment of an independent chair."
Hans Hirt, at Hermes, said: "News Corp has still not sufficiently addressed shareholder concerns about its board structure and corporate culture highlighted at last year's annual meeting. The time is right for the company to appoint an independent chair in order to rebuild trust, and ensure that the interests of all investors are more properly represented."
Both the LAPFF and Hermes demanded change at the 2011 annual meeting, when 35 per cent of votes were cast against the re-election to the board of James Murdoch and 14 per cent opposed Rupert Murdoch.
However, the Murdoch family controls 40 per cent of the voting shares in News Corp, making it is difficult for rebel investors to push for change.
Rupert Murdoch has resisted calls to relinquish his dual role in the main TV and movie business, but he intends to be only chairman of the publishing arm following its demerger.