The action stems from the discovery of �150m worth of heroin by customs officers in Felixstowe in 1993.

Brian Charrington, from Middlesbrough, was arrested and then tried on charges connected to the drugs discovery.

Case collapsed

But the case against him collapsed when two Cleveland detectives testified that it was his tip-off that led to the discovery of the drugs.

That led to an investigation by Thames Valley Police, whose findings were never made public, and then to an internal inquiry into the Cleveland force under the auspices of the Police Complaints Authority.

Disciplinary notices were later served against four officers, one of whom has already been suspended.

The disciplinary action is unconnected to another ongoing inquiry into allegations of corruption in Middlesbrough CID.