The officer, based at Mountjoy prison, was recently stopped by gardai for a routine traffic offence in west Dublin.

When gardai checked the tax and insurance discs on his private car, they discovered that the details were registered to the Irish Prison Service.

The man said he was an official with the prison service but a garda investigation has determined that he had fraudulently obtained the discs.

It is suspected that he photocopied the tax and insurance discs from an official prison vehicle and then put the photocopies, which are described as being of high quality, into his own car. The man believed that if he ever encountered a garda checkpoint he would be waved straight through because his details were all up to date.

It was only when he was stopped by a garda patrol car that the scam came to light. It is not clear how long the prison officer had been carrying out the alleged fraud but it is suspected that it could have been a number of years.

Gardai have been liaising with the prison service and a file on the alleged fraud is currently with the DPP.