An alliance of media businesses opposed to Rupert Murdoch's bid to take full control of BSkyB said it is "fanciful" to hope Sky News will be kept independent after the proposed takeover.
The coalition - including BT, Guardian Media Group, Associated Newspapers, Trinity Mirror, Northcliffe Media and the Telegraph Media Group - argued that Culture Secretary Jeremy Hunt's plans to wave through the News Corp takeover are flawed.
In a legal submission to the Department for Culture, Media and Sport, the group said Hunt's proposed decision breaks precedent and goes against regulatory advice, claiming News Corp's undertakings will not address concerns over media plurality.
The media business submission to the DCMS came to light the same day as results of a survey commissioned by campaign network Avaaz suggested an overwhelming majority of Britons opposed News Corp's move for BSkyB.
Details of the DCMS submission follow a Financial Times report suggesting the alliance of media businesses has privately admitted it has virtually no chance of success in blocking Murdoch's plans.
It is thought they have not been able to reach agreement on whether to go ahead with a judicial review, although the alliance is not said to have reached a decision yet.
Hunt said earlier this month he was minded to back News Corp's proposals to spin off Sky News as part of any deal to buy the remaining 61 per cent in BSkyB it does not already own.
The media giant offered to make the channel into a separate independent company and subsidise it for a decade.
Hunt launched a 15-day consultation on the undertakings before making his final decision, with the deadline closing yesterday at midday.
The media alliance will have three months from the final decision to launch a judicial review.
Its submission claims the planned Sky News spin-off does not address Ofcom's main objection - that the deal would reduce media diversity - saying it would remain financially dependent on BSkyB.
"It is fanciful to expect that Sky News will enjoy any meaningful independence allowing it to offer a separate contribution to news plurality," according to the submission.
It added: "Instead the editors and directors of Sky News will be acutely aware that the viability of the company - and therefore their own job security - depends entirely on maintaining the approval of News Corporation."
The DCMS said it received more than 38,000 responses to the consultation.
Lord John Prescott waded into the debate last Tuesday, sending a letter to Hunt outlining his concerns over the proposed deal.
He called on the Government to delay its decision until inquiries into the phone hacking investigation are completed.