For more than five years Rupert Murdoch and his most trusted executives told the world that a rogue reporter and a rogue private detective were responsible for hacking phones for the News of the World. Reporter Sarah Ferguson investigates that claim and reveals the links between Murdoch's newspapers and the British criminal world going back two decades.

What do you do when you're a journalist with an editor demanding an exclusive story to put on the front page? At Britain's now defunct News of the World you employed a foul-mouthed private investigator with a criminal record to get you information that would provide you with a scoop.

Phone hacking was a speciality but there were other methods too, including corrupting police who would provide the kind of private information guaranteed to win the reporter a prime spot in the paper.

This week on Four Corners, Sarah Ferguson tells the story of a key private investigator at the heart of the scandals that have set Rupert Murdoch's empire rocking on its axis. Detailing records of police surveillance and interviews with people who had been targeted by the investigator Ferguson pieces together how he worked.

As the investigation unfolds it becomes clear that phone hacking and illegal information theft were not done on behalf of one "rogue" reporter or one newspaper. Instead, the evidence suggests these surveillance activities were being done on an industrial scale - sometimes by people with criminal backgrounds - for anyone who had the cash to pay for it. As Tony Blair's former press secretary, Alastair Campbell, told Four Corners:

"It seems they were in a sense replacing journalists... possibly to cut costs, but the other reason you assume is because it meant the private detectives could do things the journalists can't."

Campbell has good reason to make such a claim. Four Corners has been told by a News insider that the practice of phone hacking and the gathering of illegal information was so widely accepted that at the News of the World competing sections of the paper used different private investigators to do their dirty work.

Meanwhile, News executives stuck to the company line of one rogue reporter. As one British MP puts it:

"You know what they say about lies: if you say it loud enough and often enough people begin to believe it and they nearly got away with it."

One reason they were able to get away with it for so long was that the British police refused to investigate the extent of the potential criminal activity. Why were they reluctant? According to one person who found himself the victim of illicit surveillance, the answer is clear:

"What happened was that the News of the World or News International more generally managed to get its filthy, slimy tentacles in every nook and cranny of the Metropolitan police and to all intents and purpose that corrupted it."

As the British parliament prepares to reopen its hearings, one question resonates throughout the News empire: how far up the corporate ladder did the knowledge and approval to pay for these services go?

'Bad News', presented by Kerry O'Brien, goes to air on Monday 29th August at 8.30pm on ABC1. The program is replayed on Tuesday 30th August at 11.35pm. It can also be seen on ABC News 24 at 8.00pm on Saturdays, on ABC iview and at abc.net.au/4corners.