The world’s most powerful proxy advisory service, Institutional Shareholders Services, have released a report backing my shareholder resolution attacking Rupert Murdoch’s gerrymander at News Corporation.

The ISS report has gone to more than 500 institutional shareholders worldwide and many of them will now vote against the maintenance of the system which sees 70% of all News Corp shares stripped of the vote.

ISS itself is very secretive so we haven’t seen the detail but no doubt some journalist will get hold of the report and break the story tomorrow. Any institution who pays $57,000 a year for the ISS reports on the ASX300 are welcome to drop a copy to [email protected].

The big question now is exactly how much of a protest vote Rupert will suffer, even with unanimous board support for the system that allows the Murdoch family to control 40% of the votes at News Corp and just 15% of the total shares.

The debacle over BSkyB’s $2.25 billion investment in ITV is a classic example of the problems that flow from giving one empire builder too much power. A forced sale by the British Government would crystallise a $560 million loss. Rupert Murdoch is chairman of BSkyB and his son James is chief executive, even though the Murdoch family only has a 5.5% economic interest in the company.

ISS don’t lose many battles. They rolled Rio Tinto’s proposed change to its constitution last year and gave booming miners Zinifex and Oxiana black-eyes last year when more than 40% of votes cast opposed their respective remuneration reports.

Even the all powerful Macquarie Bank lobbying machine failed to stop an increase in the “against” vote on its remuneration report from 5% in 2006 to 21.44% this year after ISS abandoned its support.

So, how do we measure success at next month’s AGM in New York? Getting support from 50% of the independent News Corp shares would be fabulous as would an overall “for” vote of more than 20%.

Here is a list of the board-endorsed News Corp resolutions which have received “against” votes in excess of 20% since 2000:

Options to non-executive directors in 2003: Withdrawn after majority of proxies against

Options to executives in 2000: For 392.7m, against 253.43m (39.22%)

Options to executives in 2002: For 472.57m, against 260.78m (35.56%)

Options to non-executive directors in 2002: For 472.57m, against 236.19m (33.32%)

Pay rise for non-executive directors in 2005: For 333m, against 133m (30%)

Options for Rupert Murdoch in 2000: For 478.47m, against 112m ( 20.32%)

Options to executives in 2001: For 501.77m, against 134.26m (21.11%)

Check out the four Mayne Report videoblogs on Rupert.