You could argue that there is no need for additional regulation. It is a criminal offence to pay police officers for information or favours - ever since 1901. It is a criminal offence to listen to private voice mails. It is certainly a criminal offence to delete voicemail messages and therefore potentially hinder a murder investigation.
All that is required is for Editors of most especially the tabloid rags, who specialise in turning over rocks in the hope of finding something underneath, to be rigorous in checking the source of the stories, and rejecting those obtained through illegal means, as well as penalising those journos who involve themselves in such methods.
The shocking aspects of this case is not just the thought of these cynical, amoral excuses for human beings listening into the private grief and hopes of people in the hope of finding something juicy, it is some of the peripheral stuff - there was ( and still might be) effectively an industrial scale bribery of metropolitan police officers. It has been alleged that News of the World Reporters and indirectly Rebekah Brooks, helped 2 private detectives who were being investigated on the suspicion of the murder of their business partner to find out personal details and stake out the chief investigating officer on the police force!
This is not journalism - this is sanctioned criminality by individuals totally corrupted by their own power and influence.