LONDON, July 6 - British Prime Minister David Cameron on Wednesday called for an official inquiry into a phone hacking scandal at Rupert Murdoch's News International that has prompted national outrage.

We do need to have an inquiry, possibly inquiries, into what has happened, Cameron told parliament. People had been revolted by the affair, in which journalists were said to have tapped into the mobile phone of an abducted girl who was later found to have been murdered.

The government has been under increasing pressure to hold an inquiry after allegations of phone hacking against the top-selling tabloid News of the World spread beyond politicians and celebrities to victims of crime.

British lawmakers will later on Wednesday hold an emergency debate over the scandal that has prompted calls for the resignation of a Murdoch executive.

Relatives of people killed in London's 7/7 bombings in 2005 said police had told them their voicemail messages may have been intercepted by the Sunday paper.

Graham Foulkes, whose son David was one of 52 people who died in the bombings, told BBC radio on Wednesday he was contacted by police after they found his private contact details on a list as part of the investigation into hacking claims.

He said that after the 2005 explosions his family did not have any news of David for quite some days.

...we were using the phone frantically trying to get information about David and where he may have been and ... talking very intimately about very personal issues, and the thought that these guys may have been listening to that is just horrendous, he said.

Three hours have been cleared for Wednesday's parliamentary debate, in which politicians may call for a national boycott of the News of the World until Murdoch confidante Rebekah Brooks, its former editor and a friend of Cameron, resigns.

The debate is likely to embarrass Cameron, already under fire for hiring former News of the World editor Andy Coulson as his communications director. Cameron regularly entertains Brooks and her husband at his country home.

Pressure is also mounting on News International, the British newspaper arm of Murdoch media empire News Corp, and comes at an awkward time for the conglomerate as it seeks government approval to take over satellite broadcaster BSkyB.

Car firm Ford said it would pull advertising from the News of the World until it saw how it deals with the matter, while Virgin Holidays and Halifax said it would not be advertising in it this Sunday.

Other companies said they were reviewing the situation.

Internet campaigns have sprung up urging readers to boycott the paper which, if successful, could prove more damaging to Britain's best-selling Sunday paper then any political condemnation.

Sales of News Corp's Sun newspaper never recovered in the city of Liverpool after it offended football fans in the wake of a stadium disaster more than 20 years ago in which 96 people died.

TWISTS AND TURNS

News International, which also publishes the Times, said on Tuesday night that new information had recently been provided to police. The BBC said the material related to emails appearing to show payments were made to police in the past for information and were authorized by Coulson.

Full and continuing cooperation has been provided to the police since the current investigation started in January 2011, it said in a statement.

Commentators suggested information about the payments had been released to deflect attention from Brooks.

Coulson resigned as News of the World editor in 2007, just before the paper's editor responsible for covering the British royal family was jailed for intercepting mobile phone messages, but he has always insisted he knew nothing about the phone hacking.

Coulson was later hired by Cameron but resigned from that position earlier this year as the hacking claims resurfaced.

It is not the first time a News Corp paper has been linked to police payments. In 2003, Brooks, then editor of the Sun, told a parliamentary committee her paper paid police for information. News International later said this was not company practice.

Police have been criticized for being slow to investigate the phone-hacking claims but reject suggestions this was because of alleged payments to officers.

Lawmakers have said in the past they feared criticizing any of the News Corp papers because of fears their own private lives might be exposed.

QUESTIONS FOR PM

Though the phone hacking saga has been bubbling for some time it is only this week -- when it emerged investigators may have accessed voicemail messages of crime victims, not just well-known figures -- that the affair captured much wider attention.

The Guardian said police investigating the phone-hacking claims were now turning their attention to all high-profile cases involving the murder or abduction of children since 2001.

The parents of two murdered schoolgirls in a highly publicized case dating back to Brooks's News of the World editorship have been visited by police investigating the phone-hacking affair.

Ed Miliband, leader of the opposition Labour Party, said Brooks should consider her position as News International chief executive in light of the allegations.

Brooks, 43, who has worked for Murdoch for nearly half her life, was previously seen as untouchable because of her close relationship with the News Corp chairman and chief executive.

Simon Greenberg, director of corporate affairs at News International, said that if the allegations turned out to be true they would not be tolerated.

...we would need to identify the individuals involved who were directly involved in either commissioning or dealing with this situation, he told BBC radio.

Asked if that would have serious implications for people on the paper, Greenberg said: Yes it would. But we've obviously got to establish the full facts.

Media commentator Stephen Barnett said Brooks' position seemed untenable but that Murdoch would likely support her.

Leaving her in the job is like putting an alcoholic in charge of a brewery, he told Reuters.

However if she has 100 percent backing of Rupert Murdoch, which is the word coming out of News Corp, then clearly she is untouchable and more importantly it shows that Murdoch himself thinks the company is untouchable.

Murdoch transformed the British press landscape in the 1980s during Margaret Thatcher's years as prime minister, bringing in new technology and confronting printers' and journalists' unions.

Seen as one of the world's most powerful men, Murdoch is currently trying to secure the takeover of broadcaster BSkyB, in a deal expected to be worth at least $14 billion.

The hacking revelations are unlikely to derail that deal since approvals are focused on whether the takeover will give Murdoch too much power over the British media and the government has said it does not believe it will.

(Additional reporting by Georgina Prodhan, Olesya Dmitracova and Stefano Ambrogi; Editing by Giles Elgood)

(Writing by Jodie Ginsberg)

Phone Hacking