Mulcaire was jailed in 2007 after admitting to phone hacking while he was working for the defunct Sunday tabloid. However, he has now said that he was effectively an "employee" of the News of the World, who was told to act "on the instructions of others".
In a strongly worded statement issued by his lawyer, Mulcaire said that any suggestion that he may have acted "unilaterally" was "untrue".
"Glenn Mulcaire has already expressed his sincere regret to those who have been hurt and affected by his activities and he repeats that apology most sincerely," said his lawyer.
"He was effectively employed by News of the World from 2002 to carry out his role as a private investigator. As he accepted when he pleaded guilty in 2007 to charges of phone interception he admits that his role did include phone hacking.
"As an employee he acted on the instructions of others. There were also occasions when he understood his instructions were from those who genuinely wished to assist in solving crimes.
"Any suggestion that he acted in such matters unilaterally is untrue. In the light of the ongoing police investigation, he cannot say any more."
Earlier in the month, the private investigator apologised to all those who have been "hurt or upset" by his role in the News of the World phone hacking scandal.
He has faced police questions over his involvement in the alleged hacking of the phones of murdered schoolgirl Milly Dowler, the relatives of victims of the 7/7 London bombings and grieving families of dead soldiers.
Yesterday, The Guardian reported that police had informed Sara Payne, whose 8-year-old daughter Sarah was murdered in 2000, that her details were found in notes compiled by Mulcaire.
The revelation that Payne's phone may have been hacked by the News of the World was made all the more shocking as the paper had been a vocal supporter of her Sarah's Law child protection campaign.
Former News of the World deputy editor Paul Connew has said that this latest phone hacking allegation would send "seismic waves of disgust through the country".
However, he also said that he would be surprised if former News of the World editor Rebekah Brooks knew about the hacking of Sara Payne's phone.