Detectives to examine every case involving attacks on children since 2001 in response to Milly Dowler phone hacking

Police officers investigating phone hacking by the News of the World are turning their attention to examine every high-profile case involving the murder, abduction or attack on any child since 2001 in response to the revelation that journalists from the tabloid newspaper hacked into the voicemail messages of the murdered schoolgirl Milly Dowler.

The move is a direct response to the Guardian's exclusive story on Mondaythat a private investigator working for the News International tabloid, Glenn Mulcaire, caused her parents to wrongly believe she was still alive – and interfered with police inquiries into her disappearance – by hacking into the teenager's mobile phone and deleting messages.

The case of Madeleine McCann is expected to be one of the first to be re-examined by detectives from Scotland Yard's new inquiry into the phone hacking, Operation Weeting. Other cases likely to be re-examined include 15-year-old Danielle Jones, who was abducted and murdered in East Tilbury, Essex, in 2001 by her uncle, Stuart Campbell.

Officers from Operation Weeting have already told the parents of the girls killed in Soham in 2002 by Ian Huntley that their mobiles had been hacked. Documents seized by the Metropolitan police in a 2006 raid on Mulcaire's home show he targeted Leslie Chapman, the father of Jessica Chapman.

It is understood the name "Greg" appeared in the corner of notes taken by Mulcaire – believed to be a reference to the News of the World's former assistant editor (news) Greg Miskiw. It is thought that parents of the other murdered girl, Holly Wells, were also targeted.

Police officers will trawl through their collection of 11,000 pages of notes kept by Mulcaire, and seized from him in 2006, when he and the News of the World's royal editor, Clive Goodman, were jailed for hacking into mobile phones belonging to aides to Prince William and Harry and other members of the royal household.

Mulcaire issued a public apology on Tuesday to all those hurt or upset by his activities, saying that after the developments of the past 24 hours he had to "break his silence". He said: "I want to apologise to anybody who was hurt or upset by what I have done. I've been to court. I've pleaded guilty. And I've gone to prison and been punished. I still face the possibility of further criminal prosecution.

"Working for the News of the World was never easy. There was relentless pressure. There was a constant demand for results. I knew what we did pushed the limits ethically. But, at the time, I didn't understand that I had broken the law at all."

News of the impending police action capped a dramatic day of developments in the News of the World phone-hacking scandal.

Throughout the day pressure intensified on the Rupert Murdoch-owned newspaper and, in particular, its former editor and now News International chief executive, Rebekah Brooks – who insisted she knew nothing of the Dowler hacking allegations. She was the editor of the News of the World at the time the hacking of Milly Dowler's phone messages took place.

The media regulator, Ofcom, is understood to be ready to examine whether News Corporation directors would be "fit and proper persons" to own BSkyB – if any senior employees at News Corporation or its UK arm, News International, were charged with hacking-related offences.

Rupert Murdoch's News Corporation is closing in on winning regulatory approval for its proposed £8bn-plus takeover of the 61% of BSkyB it does not own. Sources close to the culture secretary Jeremy Hunt, who will decide on the issue, insisted he could not take phone hacking into account in a decision that is focused on "media plurality".

Meanwhile a string of high-profile companies – including Ford, npower, Halifax, T-Mobile and Orange – said they would be reviewing or withdrawing their advertising in the News of the World.

These five brands are estimated to account for more than £2m worth of advertising in the tabloid in the past year. T-Mobile and Orange are thought to have spent an estimated £1.5m between them.

Ford said it would be using "alternative media within and outside News International Group instead of placing Ford advertising in the News of the World" while it awaited the outcome of an internal investigation.

The company added: "Ford is a company which cares about the standards of behaviour of its own people and those it deals with externally."

Halifax said it was "considering our options" about advertising in the News of the World, adding: "We are sensitive to the views of our customers and will take them into account."

Calls for boycotts of the News of the World appeared on Twitter and Facebook, and companies came under sustained pressure to pull their advertising from it.

Those wishing to direct their fury at the firms who advertise through the News of the World were provided with a one-stop page where they could automatically tweet their concerns to companies such as the Co-operative, easyJet, Butlins and Renault. Others went further, calling for direct boycotts of the firms unless they took their advertising money elsewhere.

John Bercow, the speaker of Commons, granted a rare emergency debate – which will happen on Wednesday – into calls for a public inquiry into phone hacking by News International journalists, and whether there was a potential cover-up by its senior executives.

Ministers in the Commons opposed the emergency debate but, in what will be seen as another show of force by Bercow, he accepted arguments in favour put by the Labour MP Chris Bryant.

The Labour leader, Ed Miliband, said Brooks needed to "examine her conscience" and that he was sure that she would because "this happened on her watch".

Although his words were Labour's strongest intervention so far on the phone-hacking crisis, the party is still undecided about whether to put forward a substantive motion calling for a public inquiry that could be subject to a vote or amendment.

In the first sign of potential coalition tension of the Conservative Hunt's planned approval of the Murdoch BSkyB deal, Tim Farron, the president of the Liberal Democrats, told BBC Radio 4's World at Oneon Tuesday: "I ask myself, is Rupert Murdoch a fit and proper person to own any more of the media market? Well, certainly not." The Milly Dowler revelations were the "tip of the iceberg", he added.

Channel 4 News reported that Brooks was confronted by the Met in 2002 about the fact a senior detective investigating the murder of a private investigator, Daniel Morgan, was targeted by Mulcaire on behalf of the News of the World. The main suspect in the case, which was being led by Detective Superintendent David Cook, was a man with close links to the News of the World.

Cook and his wife, Jackie Haines, were told by Scotland Yard in April this year their mobile phone numbers and payroll details had been found in Mulcaire's notebook. News International said it could not confirm or deny whether Brooks had ever attended such a meeting.

Lady Buscombe, the chairman of the Press Complaints Commission, said she was lied to by the News of the World over phone hacking.

"There's only so much we can do when people are lying to us. We know now that I was not being given the truth by the News of the World," she told the BBC's Daily Politics.

Brooks emailed employees at News International to insist she knew nothing about phone hacking: "It is inconceivable that I knew or worse, sanctioned these appalling allegations. I am aware of the speculation about my position.

"Therefore it is important you all know that as chief executive, I am determined to lead the company to ensure we do the right thing and resolve these serious issues."

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