Families of July 7 2005 bombing victims have been told they may have been targeted by phone hackers as MPs prepare to debate the scandal.
The new claims come after police confirmed that the parents of murdered Soham schoolgirls Holly Wells and Jessica Chapman were contacted by officers on the News of the World hacking inquiry, and after allegations that the phone of murder victim Milly Dowler was hacked.
Glenn Mulcaire, the private investigator employed by the Sunday tabloid who is alleged to have illegally accessed Milly's voicemail messages after she went missing, has apologised for any hurt he caused. Mulcaire, who made no direct reference to the hacking of the schoolgirl's phone, said he had never intended to interfere with any police inquiry.
The pressure intensified on Tuesday night as sources confirmed "several" bereaved families of those killed in the July 7 2005 bombings were feared to have been affected.
Graham Foulkes, whose 22-year-old son David was among the 52 people killed, was among those warned by a senior detective that they featured on a list of potential hacking victims. He told BBC News channel that the thought of someone listening in to his phone calls was "just horrendous".
News International chief executive Rebekah Brooks is likely to face new calls for her resignation at Wednesday's three-hour emergency Commons session, when MPs will consider whether there should be a public inquiry into the saga.
Motor giant Ford said it was suspending advertising with the News of the World. Two other leading companies, Npower and the Halifax, confirmed they were also considering whether to continue advertising with the paper amid a rising tide of anger at its alleged conduct.
Ms Brooks has pledged her "full co-operation" with the police inquiry into the claims, which date back to her time as the paper's editor. She said she was "sickened" by the allegations and promised the "strongest possible action" against those responsible. She insisted she had known nothing of the alleged actions of a private investigator working for the paper and made clear she had no intention of standing down from News International.
Her comments, however, did little to assuage the growing chorus of demands for her to consider her position and for a full-scale public inquiry into the conduct of the press and the way that it is regulated.
The condemnation was led by David Cameron who described the allegations that a private detective hacked into 13-year-old Milly's voicemail messages while police were still trying to find her as "really appalling", while Labour leader Ed Miliband said there should be a public inquiry once the police investigation was complete.