In a statement issued to the BBC, Mulcaire's solicitor said that his client "did not delete messages and had no reason to do so".
Yesterday, the parents of Milly Dowler told an inquiry into press ethics in London of the euphoria they felt after finding that voicemails had been deleted on their daughter's phone after she went missing in 2002.
Sally and Bob Dowler falsely thought Milly was alive, but later found out that the messages had actually been deleted by whoever hacked into her phone.
Ever since the news of the hacking broke in July this year, widespread reports have indicated that Mulcaire, who was jailed for hacking in 2007 with News of the World royal editor Clive Goodman, had listened to the intercepted voice messages and deleted them.
However, his statement - given to BBC Radio 4's PM programme - read: "Glenn Mulcaire has previously expressed his sincere personal sympathy for the Dowler family. Because of the ongoing criminal investigation, it is not possible for him to say much at this time.
"However, he fully supports the recent agreement by Surrey Police to disclose relevant documents from 2002 concerning voicemail interception of Milly Dowler's mobile phone.
"He is confident that they will shed light on the actions he took then and the basis of them. Further, he confirms that he did not delete messages and had no reason to do so."
"Whether he listened to the messages and wiped messages out or whether somebody else was wiping messages out to create more room for more messages to be left, is one of the points the police will undoubtedly have to investigate and explore," he told the BBC.
Lewis added: "Milly Dowler's phone wasn't registered, it was a pay-as-you-go, so Glenn Mulcaire would have found out the phone number - and one has to question where details of the phone number came from."
Sally and Bob Dowler also believe that their own mobile phones were hacked, after the News of the World learned of plans to reconstruct their daughter's final movements, and intruded on a "very, very private grief moment".
Also yesterday, the Daily Mail strongly denied claims by actor Hugh Grant at the inquiry that information taken from hacking his phone was used for story on his relationship with Jemima Khan.
Comedian Steve Coogan, supermodel Elle Macpherson's former business adviser Mary-Ellen Field, and former Premiership footballer Garry Flitcroft will give evidence today at the inquiry.