Private investigator Glenn Mulcaire has lost a Supreme Court fight to keep the identity of the person who instructed him to intercept messages a secret.
Mulcaire, who worked for the News of the World, had asked the Supreme Court to rule on whether he must disclose details about who instructed him.
Mulcaire said his lawyers advised him that he should not have to give "potentially incriminating answers" to questions asked in civil litigation at the High Court, and the appeal was made to protect his "legitimate legal interests".
Five years ago Mulcaire and former News of the World royal editor Clive Goodman were jailed after the Old Bailey heard that they plotted to hack into royal aides' telephone messages.
At Britain's highest court on Wednesday the five justices unanimously dismissed his appeal.