In a sign of the increasing severity of the situation, House of Commons speaker John Bercow has sanctioned a rare emergency debate in the chamber today. At the same time as a campaign for a public inquiry is launched in the House of Lords, politicians in the Commons will call on David Cameron to take action in response to the mounting allegations.
The recent escalation in the phone hacking scandal began on Monday, when the Guardian reported that the phone of murdered teenager Milly Dowler had been hacked by a private investigator working for the News of the World while she was missing.
It emerged yesterday that Metropolitan police officers have contacted the families of Holly Wells and Jessica Chapman, who were murdered by Ian Huntley in Soham in 2002, the same year as Dowler, to notify them that their phones may have been accessed by the tabloid.
Detectives working on the Operation Weeting phone hacking investigation have also contacted families of the vicitims of the 7 July bombings, who may have been victims.
At the time of the 7 July attacks, the editor of the News of the World was Andy Coulson, who went on to become David Cameron's director of communications but resigned earlier this year amid mounting evidence that phone hacking was widespread at the title during his editorship.
Pressure has increased on his predecessor Rebekah Brooks, who was editor during the Milly Dowler and Soham murders cases, and who spearheaded the newspaper's campaign for "Sarah's Law" following the abduction and murder of eight-year-old Sarah Payne in 2000.
Police have reportedly now widened the net to examine every high-profile murder of a child in the UK since 2001.
Brooks said yesterday that she was "aware of the speculation" surrounding her position but said it was "inconceivable" that she knew about the Dowler's phone being hacked and would not step down.
She may now face increasing pressure to do so, however, as major brands announced they are reviewing their advertising with the News of the World.
Car manufacturer Ford has pulled its adverts from the tabloid already, saying yesterday in a statement that, while an investigation was ongoing, it would be using "alternative media within and outside News International group instead of placing Ford advertising in the News of the World".
nPower, npower, Halifax, T-Mobile and Orange have also announced that they will be reviewing their advertising in the newspaper.
Halifax said that it was "sensitive to the views of our customers and will take them into account", and nPower stated that it was "reviewing its options".
T-Mobile and Orange issued similar statements, both saying they were "reviewing our advertising position with the News of the World, following the recent allegations, and await the outcome of the ongoing police investigation".