The Metropolitan Police unlawfully tapped phone calls of one of their own senior officers, the BBC has learned.
Mr Dizaei has not commented on the tribunal's ruling
The force listened to calls made by Chief Superintendent Ali Dizaei, legal adviser to the National Black Police Association (NBPA).
The interception was ruled unlawful by the Investigatory Powers Tribunal.
The NPBA said the tapping included calls when Mr Dizaei gave advice to black and Asian colleagues in dispute with their own forces.
It said Mr Dizaei's calls were tapped during Operation Helios, in which the Met recorded 3,500 private conversations.
This was an investigation into Mr Dizaei, who was under suspicion of being corrupt. He was cleared of all charges brought against him.
The wire tap complaints were brought by the NBPA because they felt that some calls were legally privileged.
Mr Dizaei has not commented on the ruling but a spokesman for the association said it would be seeking compensation for members.
The Metropolitan Police said it was reviewing the findings of the tribunal.
The Metropolitan Police Authority also said it would be "urgently" examining the ruling.
A spokesman said: "The findings of unlawful action by the police service itself is of great concern.
"The MPA will want to be satisfied that individuals are held to account for any wrongdoing and that action is taken to prevent any recurrence of illegal interception."
Shami Chakrabarti, director of human rights organisation Liberty, said: "Telephone tapping is a vital crime-fighting tool, but there is far too much scope for abuses within the current system."
The BBC's Barnie Choudhury said the case was an embarrassment for the Met, which was accused of being "institutionally racist" during the Stephen Lawrence inquiry.