Alan Rusbridger, the editor-in-chief of the Guardian, today stepped into the debate over whether Rupert Murdoch's News Corporation should be allowed to take full control of BSkyB, by warning of the "chilling effect" that "one large media company can have on public life".

Giving a lecture in Murdoch's native Australia, Rusbridger said that the revelations of phone hacking at the News of the World illustrated "the nature of the problem" when one media group becomes too powerful in the UK.

The controversy, Rusbridger said, "raises questions which are not so much about hacking, troubling as those are, but about how other forces in society – whether it is other media organisations, the police, the regulator or parliament itself – behave when faced with the muscle of a very large, very powerful and sometimes very aggressive media group".

He added that "something is dangerously out of kilter" when MPs such as Adam Price on the Commons culture, media and sport select committee confess they have been "held back" from probing into News Corporation's affairs because of "fear of what that company might do to them" – or when former employees are "too frightened to speak publicly about what they know" .

In June, News Corporation proposed an £8bn buyout of the 61% of satellite broadcaster BSkyB it does not already own, a deal that would bring together the largest newspaper group in the UK, with nearly 40% of the average daily sale with the largest broadcaster by turnover. Combined, the two companies would have a turnover of £7.5bn, compared to the BBC's £4.8bn.

Rusbridger queried whether it could be "good public policy to allow a still greater concentration of power across not just one wing of the Fourth Estate but two". He said that while it was possible to come up with "all kinds of metrics" to justify the merger on competition grounds, "it would still feel wrong".

He said that the argument about the proposed buyout was not about the individual merits of Rupert Murdoch as a media owner, warning instead that "there's no one I would want to have that much power" – whether it was the BBC, the moderator of the Church of Scotland or even Sir David Attenborough.

Last month, a group of competing newspaper groups and broadcasters – including Guardian Media Group, publisher of the Guardian – signed a letter calling on Vince Cable, the business secretary, to refer the proposed merger to Ofcom on "public interest" grounds. The other signatories included the companies behind the Daily Telegraph, the Daily Mail and the Daily Mirror, as well as BT, Channel 4 and the BBC. Cable referred the bid to Ofcom in early November, after News Corp had formally notified the European Commission of the proposed takeover.

The deadline for submissions to Ofcom is today, with a range of media groups and thousands of individuals expected to put their views forward – including the members of the alliance of newspaper owners and broadcasters opposed to the deal. However, the BBC has decided to drop out of the group, amid a row at the corporation over whether it is legitimate for the public broadcaster to take a hostile stand against any rival.

Rusbridger's speech in Sydney – the annual Andrew Olle lecture, titled The Splintering of the Fourth Estate – touched on a range of other subjects about the future of newspapers in the digital era. Worrying that the balance of power in the media was beginning "to teeter", as "digital eats into the press" and an angry press "turns its fire on public broadcasters" such as the BBC, Rusbridger said that the future of all media appeared dependent on subsidy.

The subsidy model was critical to funding the BBC – "the finest news operation in the world" – but he added that such financial support also came from other sources, such as advertising, wealthy individuals or a profitable sister company.

"If you include advertising, then we're all members of what some like to call the 'subsidariat'," Rusbridger said, referring to a concept introduced by Paul Dacre, the editor-in-chief of the Mail titles, who used it as a notion to criticise newspapers that did not make a profit.

The wide-ranging speech also encompassed a lengthy exposition of the virtues of Twitter, as an example of the "power of open, or social media" – a "new journalism" that has an "engaged" relationship with "readers, sources and advertisers".

Rusbridger said the approach helped traffic at the Guardian's websites to reach just over 2 million daily unique browsers – but while he contrasted the figure with the relatively low number achieved by the Times website, which sits behind a newly launched paywall, the editor said that "the jury on the relative financial models for different approaches will remain out for a while yet".

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