Rupert Murdoch's ambition to expand his media empire still further could be killed off by MPs this week after Labour announced plans for a Commons vote to thwart his bid for BSkyB.

The move comes amid a mood of continuing public uproar over the phone-hacking scandal, which is now threatening to destabilise David Cameron's government.

The vote will present the coalition with a major test of unity as the Labour leader, Ed Miliband, seeks cross-party support for a motion in parliament which would halt progress on the takeover until the criminal investigation into the News of the World is completed.

With many Liberal Democrats and Tory MPs deeply uneasy about Murdoch gaining an even bigger slice of the UK media market – and still incensed by the behaviour of News Corp executives – Labour is optimistic it can mobilise enough support to achieve a majority.

Miliband will appear on the BBC's Andrew Marr Show on Sunday to announce his plan and to begin his push for support across all the major parties. He will lay the motion tomorrow and the debate and vote will be on Wednesday.

If he is successful, the Labour move will drive a wedge between the coalition parties and leave Murdoch's takeover ambition in tatters – because the police inquiry could take several years.

The parliamentary debate will also give David Cameron another major headache, following the arrest on Friday of his former director of communications, Andy Coulson, who is a former editor of the News of the World.

Cameron has so far refused to intervene to block the takeover. On Friday, Cameron told a press conference: "People are also asking about the prospective BSkyB bid. As I have repeatedly said, governments must follow the proper legal processes and procedures.

"That is exactly what Jeremy Hunt, the culture secretary, is doing. His role is to take the advice of independent regulators and, as his department have made clear this morning – given the events of recent days – this will take some time."

On Saturday, Cameron was facing growing demands to take a tougher line and tell the News Corporation chairman that the bid must be withdrawn as it would only stoke the mood of public disgust at the phone-hacking scandal.

Paddy Ashdown, the former Liberal Democrat leader, told the Observer: "The public will be outraged and bewildered and trust in our politics will take yet another knock if this takeover goes ahead after what has happened.

"I think Jeremy Hunt or better still David Cameron should call in Rupert Murdoch and say that this bid is no longer welcome."

Hunt has said only that he is delaying until September his verdict on whether to allow News Corporation to proceed in its bid to take full control of BSkyB, on the basis that there had been a deluge of last-minute submissions on the deal last week.

However, the government insists that it would be unlawful to kill the deal on the basis of the latest furore, and that it must make the judgment on whether the deal would maintain media plurality.

The fallout from the scandal is now threatening to destabilise the coalition with many Liberal Democrats determined not to be associated with a government that appears unwilling to take on Murdoch.

Labour sources said that initial soundings suggested there would be strong support for the motion among Liberal Democrat and Tory MPs, as well as peers of both parties.

A Liberal Democrat source said: "The party is not happy about this deal and they would welcome the chance to act." News Corporation is in the process of trying to buy the 61% of the satellite broadcaster that it does not already own. Before the phone-hacking scandal erupted again last week, the deal had looked on course to be approved by Hunt within weeks.

But in recent days there have been calls for the media regulator Ofcom to investigate whether News Corporation is a "fit and proper" owner for BSkyB. BSkyB shares closed down 12% last week in London, but News Corp shares in New York had barely changed.

On Saturday, Downing Street said the public inquiry into criminality at the News of the World and other newspapers would start as soon as was practical, while ensuring it did not prejudice the police investigations. It will be led by a judge and have the power to call witnesses who would give their evidence under oath and in public.

The second public inquiry will seek a new framework for the regulation of the press and will be led by a panel of figures from different backgrounds.

Sir Menzies Campbell, another former Liberal Democrat leader, said it would technically be possible for Cameron or Hunt to refuse the takeover "out of hand", thereby putting the onus on Murdoch to go for a judicial review – a move he believed would further enrage the public.

However, he said there were other legal avenues that could be explored because the decision to proceed this far had been based on undertakings given by people who might no longer be judged as reliable.

Lord Oakeshott, a Liberal Democrat peer who is close to business secretary Vince Cable, has released the text of a letter to Ofcom's director, Ed Richards. In it he asked if "Ofcom is satisfied that the board of BSkyB are all now fit and proper to hold a broadcasting licence, in the light of this week's admissions of management failings by its chairman and representative of its controlling shareholder, James Murdoch, and a mountain of evidence pointing to negligence at best and criminality at worst by the senior management of News International?"

Baroness Shirley Williams, a Liberal Democrat, said she was in "no doubt whatsoever that the bid should be put on the back-burner" until the police inquiry was complete.

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