Stephens said that the police had confirmed he is among the 4,000 potential victims. His name appears in private investigator Glenn Mulcaire's notebooks, which police are currently investigating closely.
The police are contacting people whose mobile phone numbers were listed in Mulcaire's records. Stephens told Channel 4 News he contacted Scotland Yard to ask if his phone had been targeted.
He said: "I asked them if I'd been hacked - they came back to me in 90 mins and said yes. It confirmed my worst suspicions, that I was in Mulcaire's notebook".
He added: "There is nothing I can do about it but the important thing is to ascertain which client [was the target] so I can advise them. My concern is for them, not myself. Until they [police] come and see me - I don't know which client it's in connection with."
Stephens's former clients include James Hewitt, who had an affair with Princess Diana, and most recently the WikiLeaks founder Julian Assange.
Other reports say that three solicitors, including Mark Lewis, who is representing 70 alleged hacking victims including the family of murdered teenager Milly Dowler, may also have had their voicemails illegally accessed.
The Law Society has expressed serious concerns following the development, pointing out that interfering with the voicemail of a solicitor is potentially a serious offence if it has been done with the intention of undermining court action.