The row over phone-hacking at a British tabloid erupted into a national scandal on Wednesday, amid allegations that relatives of murdered children and victims of the London 2005 bombings were targeted.
After the claims sparked widespread outrage, an emergency parliamentary debate was to be held to discuss the activities at the News of the World, the top-selling Sunday newspaper owned by Rupert Murdoch's News International.
The new allegations heap pressure on two former editors of the tabloid, Andy Coulson, who went on to work for Prime Minister David Cameron until earlier this year, and Rebekah Brooks, now chief executive of News International.
Their timing is also potentially highly damaging for Murdoch's News Corp., as the government is due to decide this week whether to approve its controversial bid to take control of satellite broadcaster BSkyB.
The tabloid has been dogged by claims of phone hacking ever since its royal editor and a private investigator, Glenn Mulcaire, were jailed for the practice in 2007, and police launched a new probe into fresh allegations in January.
But where it was believed the tabloid had only hacked politicians and celebrities, it emerged this week that bereaved families, including those whose relatives were killed in the July 7, 2005 attacks, may also have been targeted.
Graham Foulkes said he believed his phone may have been hacked during the week he waited for confirmation that his son David was one of 52 people killed when suicide bombers attacked the London transport system.
"My wife and I were kind of all over the place, we were chatting to friends on the phone, in a very personal and deeply emotional context -- and the thought that somebody may have been listening to that just looking for a cheap headline is just horrendous," he told the BBC.
It has also emerged that the parents of Holly Wells and Jessica Chapman, two 10-year-olds who went missing in Soham, eastern England, in 2002 and were found murdered several weeks later, may have been targeted.
The news followed allegations on Tuesday that the News of the World hacked into the voicemail of murdered teenager Milly Dowler in the days after she went missing in 2002. Her remains were found six months later.
When her voicemail box became full, they even deleted messages to make room for new ones an action that hampered the investigation because her loved ones and police mistakenly took it as proof that Dowler was still alive, reports said.
Cameron said that if they were true, the revelations about Dowler represented a "truly dreadful act" and were "quite, quite shocking". Related article: UK media shamed by 'squalid' phone hacks claims
As chief executive of News International, Brooks also expressed her disgust in an email to staff on Tuesday, saying she was "sickened" by the revelations and they were "almost too horrific to believe".
She promised a full investigation and the "strongest possible action" against anyone found responsible.
Brooks was editor of the News of the World in 2002, but she said it was "inconceivable" that she sanctioned the hacking of Dowler's phone.
Opposition Labour leader Ed Miliband is among those calling for Brooks to consider her position, although she reportedly has Murdoch's strong backing.
Pressure is also growing on Coulson, who resigned in 2007 after Mulcaire was jailed. But he always denied wrongdoing and went on to work for Cameron as his director of communications.
However, the BBC reported late Tuesday that News International have passed emails to the police which suggest Coulson authorised illegal payments to police while he was in charge.
News International has promised to fully cooperate with the police investigation into the hacking, but there are signs that the scandal could severely damage the News of the World, the biggest earner among its papers.
Motor giant Ford has announced it was suspending advertising with the tabloid, while energy company Npower and the Halifax bank said they were considering following suit.
In a statement issued late Tuesday, the private investigator jailed in 2007, Glenn Mulcaire, apologised for his actions but said there was "relentless pressure" at the News of the World, and a "constant demand for results".