THE phone hacking scandal surrounding the News of the World has deepened after it emerged the parents of murdered Soham schoolgirls Holly Wells and Jessica Chapman have been contacted by police.

Ford has suspended advertising with the paper in the wake of the scandal, while a number of other high-profile companies, including Halifax, npower and T-Mobile, are also considering pulling accounts.

The moves followed a huge online campaign by members of the public urging advertisers to cut their ties with the paper.

Yesterday Glenn Mulcaire, the private investigator at the centre of the allegations, apologised for his part in the affair and blamed the “relentless pressure” of working for the News of the World.

The newspaper has launched an internal investigation to be led by Rebekah Brooks, the chief executive of the newspaper’s parent company, who was editor of the title at the time of the allegations.

In a statement issued last night, Mulcaire asked the media to leave his family and children alone and said: “Working for the News of the World was never easy. 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.”

Mulcaire, who was jailed in January 2007 after the Old Bailey heard he and the newspaper’s royal editor plotted to hack into royal aides’ telephone messages, issued the statement 24 hours after allegations emerged that he accessed the voicemail messages of schoolgirl Milly Dowler in the days after she went missing.

That accusation prompted Prime Minister David Cameron to say he was appalled at the “quite shocking” claims.

Labour leader Ed Miliband called on Mrs Brooks, below, to consider her position but News International insisted she would not stand down.

In a statement Mrs Brooks described the allegations as “almost too horrific to believe” and said she had launched an internal investigation.

But that move was likened to putting Adolf Hitler in charge of “cleaning up the Nazis” by the actor Hugh Grant, whose own phone was allegedly hacked.

And last night it was claimed Mrs Brooks had contacted a private detective to gain information related to the Dowler case.

As Ford announced that it had suspended advertising with the newspaper, Tesco and other advertisers also came under pressure on social media websites to pull ads and a Facebook site was set up calling for readers to boycott the paper.

The industry watchdog, the Press Complaints Commission, also said it was angry and claimed it had been lied to by the newspaper about phone hacking.

Cambridgeshire Police said that the parents of Holly and Jessica had been visited by officers investigating phone hacking allegations.

The Soham case gripped Britain in 2002 when the schoolgirls went missing on their way to buy sweets. Two weeks later they were found dead, murdered by Ian Huntley.

It is thought that the hacking allegations centre around a mobile belonging to Jessica’s father.

Milly Dowler’s parents are now suing the News of the World over claims her phone was hacked after she went missing. Bob and Sally Dowler said they had been given “false hope” their daughter could still be alive after phone messages were deleted after she vanished.

In his statement, Mulcaire added: “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. I do ask the media to leave my family and my children, who are all blameless, alone,” he said.

The allegations come as the paper’s parent company awaits a decision on whether it can take over broadcaster BSkyB. The Coalition is currently consulting on the proposed takeover.