Glenn Mulcaire’s legal team said any suggestion he may have acted unilaterally was untrue, just hours after it was alleged he targeted the mother of murdered schoolgirl Sarah Payne.
His lawyers said he acted on the instructions of others and had been “effectively employed” from 2002 onwards.
Mr Mulcaire also repeated his apology to all those who he said had been hurt by his activities.
Sara Payne said she was “very distressed and upset” after police found her details among notes compiled by the News of the World.
MPs said the scandal had hit a new low after it emerged she had been provided with a mobile phone by the Sunday tabloid, with whom she worked closely on a campaign to change the law in her daughter’s memory.
She also developed a close relationship with the former editor Rebekah Brooks, who has expressed her shock that Mrs Payne was targeted.
Mrs Payne issued a statement saying: “Notwithstanding the bad apples involved here, my faith remains solidly behind all the good people who have supported me over the last 11 years. I will never lose my faith in them. My way would be to challenge the bad apples head-on, learn from the facts and be a proactive part of stopping this from happening again.”
It also emerged yesterday a police officer involved in the Payne investigation believes his phone may have been hacked.
Detective Chief Inspector Martyn Lewis, who was second-in-command of the Sussex Police investigation into the 2000 killing, said he had reported his concerns to Scotland Yard.
Mr Mulcaire’s intervention comes just a week after the Murdoch-owned News Corp announced it had told Mr Mulcaire he would have to foot his own legal bill.
There was outrage when Rupert Murdoch and his son James revealed to MPs they were paying the fees of the investigator, jailed over hacking in 2007.
It also emerged James Murdoch could be hauled back in front of MPs after senior executives at the paper disputed the evidence he gave to a parliamentary committee.
John Whittingdale, the chairman of the Commons Culture, Media and Sport Committee, said it was likely that he would be asked back.
The committee is next due to meet in two weeks when they will discuss Mr Murdoch’s response to a series of questions sent by the committee.
The MPs also plan to write to Colin Myler and Tom Crone, the executives who disputed Mr Murdoch Jnr’s claim he had been unaware of the now infamous “for Neville” email which allegedly shows hacking was widespread at the paper.
They will also write to Harbottle and Lewis, the law firm, to ask if it can provide further evidence about the scandal now News International has revoked part of the confidentiality clauses in its contract.