A former Victorian detective has been sentenced in the Darwin Magistrates Court to 15 months in jail for serious drugs offences.

Clifton Robert Lockwood pleaded guilty to supplying an undercover policeman with more than 1,800 pseudoephedrine tablets at a Darwin casino last December.

Lockwood told the court he was trying to sell the drugs for a girlfriend and simply made a big mistake. He said he was extremely embarrassed and would never try to sell drugs again.

But the magistrate dismissed his claims and sentenced him to 15 months in prison with a non-parole period of eight months.

It is not the first time Lockwood has been in the spotlight.

He was charged with the murder of Gary Abdallah while working as a policeman in Melbourne in the late 1980s. He was acquitted of the murder five years later.