Leading article: Power that threatens both an industry and democracy

What took him so long? The Culture Secretary, Jeremy Hunt, has spent another four months considering Rupert Murdoch's proposal that his News Corp business should be allowed to take over BSkyB. Now Mr Hunt has given the go-ahead with only the smallest of additional conditions.

That may be good news for the mighty media tycoon, and the politicians of all parties who routinely pay homage at the Murdoch altar, but it is rather alarming for the health of Britain's media and its democracy. Mr Hunt will doubtless insist that he has ensured that media diversity has been secured by requiring Sky News to be hived off in a separate company with an independent chairman and directors, none of whom can have worked for the Murdoch empire in the past five years. A "monitoring trustee" will be appointed to ensure News Corp complies with its undertakings.

All of that is utterly worthless. Rupert Murdoch made similar promises when he bought the News of the World, then the Times and Sunday Times and then the Wall Street Journal. They proved wholly ineffective in protecting editorial independence, as former Murdoch editors have testified; the managing editor of the Journal, whose position was protected by the committee structure set up to secure the deal, resigned after just four months, with a handsome pay-off.

But all that is to miss the real point, which is what Ofcom did when it focused concerns on the narrowing of the plurality of media ownership. The real threat is not that Mr Murdoch might immediately increase the percentage of the population to whom he can peddle his dubious political worldview. It is that it risks extending the commercial power of a media empire which is responsible for widescale and illegal phone-hacking at the News of the World; which manifests an obsessional hatred of the BBC; and which has pioneered a style of virulently partisan right-wing television at Fox News in the United States.

This deal will be worth billions to Mr Murdoch. Alongside that, the £30m a year it will cost him to underwrite Sky News for the next decade is a small price to pay. And there is nothing to stop News Corp taking it over when that period expires. Meanwhile, the power of the giant conglomerate – with its newspaper, television and internet outlets – to fix advertising rates across a range of different media platforms will give the company a market position which verges on anti-competitive.

At a time when the economics of the industry are already tricky, the implications for the rest of the media could be disastrous. News Corp could exploit its position further by what the industry calls "cross-bundling" – offering special television deals to readers of its newspapers, and cross-promoting its services and staff. Add to that Mr Murdoch's record of predatory pricing – slashing the cover price of his papers – and other titles could be driven out of business.

A threat to media diversity is a threat to democracy, which is why a commercial media organisation of this size, which would be even larger than the BBC, would not be permissible in most other democracies. But do not expect Mr Murdoch's Conservative friends to do anything about it. Nor will Ed Miliband, who is following the example set by his predecessors Tony Blair and Gordon Brown in courting the owner of the newspapers of which the Labour party has run scared for decades. For all Vince Cable's posturing about "declaring war on Murdoch", no mainstream politician can afford to make an enemy of a man who sits at the centre of such a vast media web. And that fact alone is the perfect illustration of the dangers of one man having so much media power.