Former senior Scotland Yard officer Ali Dizaei has been told that he could have been a victim of phone hacking by the News of the World.
Detectives investigating hacking by the newspaper said a phone belonging to Mr Dizaei was called on numerous occasions in 2006, his lawyers said.
Mr Dizaei said he was "shocked" and would sue if the claims were true.
The paper's royal editor and a private investigator were jailed in 2006 for phone hacking, but inquiries continue.
Mr Dizaei was sacked by the Met after he was convicted of misconduct in public office and corruption. He was released from prison two weeks ago after he won an appeal and is now facing a re-trial.
The former senior police officer said: "I am shocked, appalled and very disappointed that this was not highlighted earlier.
"This could be the first time that it has been confirmed that a police phone may have been hacked by the News of the World."
He said the phone which the hacking allegations relate to was used for police business, which included his work as the legal adviser to the National Black Police Officers Association when he was giving "confidential information".
And a statement from Mr Dizaei's solicitor, Farooq Bajwa, said "it appears certain that Mr Dizaei will now commence legal action".
It went on: "Mr Dizaei's legal team are calling for a full public inquiry to be held following the end of the civil and criminal proceedings to ensure that the full facts of these cases be made known."
The Met Police are re-examining the entire case relating to phone hacking practices dating back to 2006, when the News of the World's former royal editor, Clive Goodman, and private investigator Glenn Mulcaire were jailed for hacking into the mobile phone voicemails of royal aides.
Since then, a series of inquiries and legal cases have been exploring just how widespread the practice was.
More and more celebrities and public figures have alleged their phones have been hacked and some have launched legal actions against the paper or the police for allegedly failing to investigate.
News International has said it will co-operate fully with the Metropolitan Police inquiry.