A lawyer who advised News International has said the company was told in 2008 there were three journalists other than Clive Goodman involved in phone hacking.
Julian Pike told the Commons culture committee he had "not done very much" to dispute the firm's claims that only "one rogue reporter" was involved.
But he insisted he was "not party to any cover-up".
Goodman was jailed in 2007 for hacking phones belonging to royal aides.
Mr Pike, who works for solicitors Farrer and Co, advised News International in its phone-hacking case with the Football Association's Gordon Taylor.
His case is seen as key to the dispute over how widespread hacking was.
Mr Taylor settled out of court with the News of the World for a reported £425,000.
But an email handed to his lawyers by the police - known as the "For Neville" email - has been at the centre of a disagreement during previous committee hearings.
There was a powerful case to support [the existence of] a culture of illegal accessing of information”
End Quote Julian Pike Solicitor
When the News of the World's royal editor Clive Goodman was jailed for hacking into phones of the royal household in 2007, the paper insisted the practice was not more widely used.Mr Pike told the committee the email was a "critical piece of evidence" relating to phone hacking.
"It was quite clear having seen the For Neville email... that there was involvement of News of the World journalists other than Goodman," he said.
The lawyer also said that in 2008, at the time of the Taylor case, the advice given to News International was that there were "three journalists other than Goodman involved in phone hacking".
"They were also advised by counsel and ourselves that there was a powerful case to support [the existence of] a culture of illegal accessing of information to get stories," he added.
Mr Pike said there was no obligation for him to report to the police that he knew phone hacking was more widespread at the News of the World than the company was claiming.
Asked what he had done to correct those claims, he said, "I'll be honest, I haven't done very much," but added that this did not cause him "any professional embarrassment".
The committee also heard from Mark Lewis, the solicitor who represents many of the alleged victims of phone hacking - including the family of Milly Dowler - and who represented Mr Taylor.
It was only the Milly Dowler case that exposed everything”
End Quote Mark Lewis Solicitor
Mr Lewis said the settlement for Mr Taylor was much higher than would have been expected in a privacy case in which no story was actually published.
He told MPs he believed that was to "hush up" the matter and encourage him not to bring any further claims or make public any further allegations.
"They didn't want it to get out," he said. "They paid my costs in full. They didn't knock a penny off - that's unheard of in litigation."
He added: "The News of the World's stance on all this has moved from one rogue reporter... to trying to present this as something that is about people who have no right to any sympathy - politicians, celebrities, sports people.
"It was only the Milly Dowler case that exposed everything. The lie that was being told by News of the World, but also all the other newspapers. That was really the scandal. It was a cover up by all the newspapers."
Mr Lewis also claimed his own phone had been hacked as recently as 2011.
Committee chairman John Whittingdale said in September he wanted to hear from Mr Pike before recalling News Corp boss James Murdoch to give further evidence.
Former News of the World legal manager Tom Crone has told MPs he is "certain" he informed Mr Murdoch about the For Neville email.
But, Mr Murdoch, who is the European chief executive of News Corporation - the parent company of News International, which owned News of the World before it was closed in July 2011 - has insisted he was never told about it.
Next week, the MPs will hear evidence from News International's former executive chairman Les Hinton.
He will appear via videolink from the United States, where he lives.