David Sherborne, the barrister representing victims of phone hacking and press intrusion, told the Leveson inquiry at the high court in London that misdemeanours at the tabloids were "systemic, flagrant and deeply entrenched", reports The Guardian.
In a scathing attack on the popular press, the QC said that the practices were done to "satisfy an insatiable public appetite for salacious gossip" as the publishers pursued big profits.
He added that the malpractices could rarely if ever be justified by the newspapers on the grounds of public interest.
Yesterday, Sherborne told the inquiry that the parents of murdered schoolgirl Milly Dowler believe the News of the World used information hacked from their mobile phones for articles that intruded into "their private grief".
At today's session, the QC said that phone hacking at the now defunct Sunday tabloid was widespread, with the intercepted information often published as "quotes from pals".
Lord Leveson's inquiry will hear evidence from a range of parties affected by alleged press intrusion, including Charlotte Church, JK Rowling, and Sheryl Gascoigne due to appear next week.
Max Mosley, who is due to appear before the inquiry next Thursday, has claimed that his son's death from a drug overdose was in part down to the family's treatment by the press following a story about the former Formula One chief's personal life.
"He was mobbed by journalists at the house even though he had written to newspaper editors asking to be left alone," said Sherborne, adding that a reporter in disguise even attempted to gain entry to Mosley's son's funeral.
Earlier in the month, the publisher of the News of the World was ordered by a court in France to pay £32,000 in costs and damages after being found guilty of violating the privacy of Mosley.
Sherborne also told the court how Kate McCann was left feeling "mentally raped" after the News of the World published details of a private diary she had written to her daughter Madeleine, who went missing in Portugal in 2007.
"On what grounds did they think they could justify such a staggering intrusion into the McCanns' privacy?" he said, adding: "There are the stories behind the headlines. This is the real, brutally real, impact this kind of journalism has."
Lawyers representing newspaper publishers, including former News of the World publisher News International, are said to have listened in silence as Sherborne issued his attack.