Mark Lewis, the lawyer for victims of phone hacking, has told the Leveson inquiry the practice went beyond the News of the World and News International.
Lewis told the probe into press ethics that he'd learned Glenn Mulcaire, the private investigator hired by the News of the World, gave lessons on how to intercept voicemail messages to a journalist who worked for Associated Newspapers.
Speaking at the inquiry in London on Wednesday, Lewis said he obtained a CD that had a phone conversation between Glenn Mulcaire and the unnamed sports reporter who at the time worked for the Evening Standard.
From Lewis' written evidence it is implied the unnamed journalist went on to work for News International at The Times.
Lewis said that phone hacking was not just practised by the News of the World and admitted he almost "felt sorry" for the tabloid and its readers.
He said the NotW had been unfortunate as Mulcaire had made the mistake of writing things down in a notebook that connected him to the paper.
Lewis also told the inquiry that the editor of the Daily Mail warned him not to suggest his paper had engaged in phone hacking.
"I was told Paul Dacre wouldn't hesitate to sue me if I suggested the Daily Mail was involved in phone hacking," he said.
Lewis said the warning was prompted by an interview he gave in which he suggested phone hacking went beyond the News of the World.
He said he took it to be a "general warning" from the tabloid.
Lewis also recounted how Daily Mail columnist Amanda Platell had unfairly attacked him for being a "greedy lawyer" when negoatiating a financial settlement from News International for the parents of murdered schoolgirl Milly Dowler.
Rupert Murdoch agreed to pay the couple £3m in compensation after it was found their phones had been hacked.
Lewis said Platell had implied the time taken to finalise the deal was that he was trying to get more money out of the Murdochs. But Lewis said this was untrue and the Mail Online was forced to remove the story from its website.
He added that journalists engaged in phone hacking thought the activity was no worse than "driving 35mph in a 30mph zone" and beleived they could do what they liked in the name of a free press, "almost as if they are above the law".
The lawyer, whose clients include the family of murdered schoolgirl Milly Dowler, whose phone was hacked by Mulcaire, said he believed illegal voicemail interception was widespread because there was no other means for journalists to get certain information.
"It is evidence-based conclusions, certainly on a civil basis, of what I am being told by clients and taking instructions from them as to whether or not stories are written that could not have got to newspapers in any other way," he said.
Lewis also told the inquiry of the moment he realised the extent of phone hacking, when he linked the convictions of Glenn Mulcaire and the former royal editor of the News of the World.
"It was a light bulb moment, a eureka moment," he said.
The parents of kidnapped Madeleine McCann are also due to give evidence to the inquiry on Wednesday.
Kate and Gerry McCann are expected to describe their anger at newspaper stories suggesting they may have been involved in the little girl's disappearance from the family's holiday flat in Portugal in May 2007.
The inquiry, sitting at the Royal Courts of Justice in central London, is also hearing evidence from Sheryl Gascoigne, the ex-wife of former England footballer Paul Gascoigne, and journalist Tom Rowland.
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