The prison in Oberhausen, North Rhine-Westphalia, was revamped into a therapy centre for mentally-ill, violent offenders in 2011. It had room for 18 prisoners and cost just over €1 million to convert.

A further €2 million was spent on 26 staff members in one year which included six security guards.

Therapy, meals, medical care, transportation and building management cost another €175,425. And €1 million was blown on furnishings and fittings.

But in 12 months from mid-2011 to mid-2012 it had a single inmate – a sexual offender from Bavaria, the West Deutsche Allgemeine Zeitung reported on Thursday.

He was joined for one week by another inmate and who was then released.

The prison has now turned into a political row with the Christian Democrats (CDU) in Oberhausen blaming the Social Democrats (SPD) for the mess.

Wilhelm Hausmann, a CDU member in the North Rhine-Westphalia state parliament, led an inquiry into  the spending.

He said the costs were an “appalling waste of taxpayers’ money” and gave Oberhausen a bad reputation.

The facility closed on December 31st 2012 and was meant to be demolished, but there are now plans to turn it into a hotel for prison visitors.

READ MORE: Berlin thieves steal 300 phones in one minute