The New South Wales corruption watchdog has found a Sydney prison guard went to work high on the drug ecstasy and supplied steroids to a colleague and a former inmate.

The Independent Commission Against Corruption says Robert Di-Bona worked two shifts at Long Bay jail while under the influence of ecstasy.

On one of those occasions he was carrying a gun because he was on tower duty.

The ICAC has also found Mr Di-Bona supplied steroids to fellow prison worker Christopher Warren and a former inmate.

It has reported that Mr Di-Bona also repeatedly used his mobile phone on duty, which is against the law.

The ICAC says the evidence obtained from electronic surveillance devices and compulsory examinations established that Mr Di-Bona had acted corruptly, so it was not necessary to hold public hearings.

It is recommending the Director of Public Prosecutions consider charging Mr Di-Bona with six offences of lying to the ICAC and that Corrective Services NSW consider dismissing him.

The ICAC has also suggested disciplinary action be taken against Mr Warren.