How are privately-run prisons performing?

There are 134 prisons in England and Wales

When it opened, in April 2012, it was one of the country's "giant jails" or "super-prisons" - a building capable of housing more than 1,600 inmates.

Its website says it aspires to be known as 'the leading prison in the world' within five years.

The opening of the £180m HMP Oakwood, Wolverhampton - and other similarly-sized prisons - has been accompanied by the closure of smaller centres up and down the country.

But, 18 months on, the results of an inspection have revealed Oakwood, which is run by G4S, is "failing to tackle drugs".

'An absolute scandal'

So how are privately-run prisons faring?

There are 134 prisons in England and Wales. Since 1992, 13 of these have been privatised.

The Ministry of Justice uses a four-point scale to rate prisons on an annual basis.

Oakwood is one of two privately-run institutions, the other being Thameside in London, to have received the lowest rating of one - signifying "overall performance is of serious concern" - in the 2012/13 ratings.

Two others - Birmingham and Bronzefield - achieved ratings of two, signifying "overall performance is of concern".

Eight achieved a rating of three. Parc in Bridgend was the only privately-run prison to receive the highest grade of four.

However, a study by a centre-right think tank Reform concluded in February that private companies are better at running prisons than the public sector.

Yet, only one of the 121 publicly-run prisons achieved the lowest rating in the 2012/13 inspections, with a further 10 achieving ratings of two.

The HM Chief Inspector of Prisons' annual report for 2011/12 suggests there has been an improvement in prison performance, with 82% of jails receiving a positive score for safety, compared with 75% in 2005/6.

Mark Leech, editor of Converse, the national prisons newspaper for England and Wales, said whether a prison was in public or private control was irrelevant.

"I don't care whose name is over the door. You will get good and bad public and private prisons," he said. "I'm much more concerned about the management of individual prisons.

"The report about Oakwood is an absolute scandal.

"I believe the Secretary of State for Justice, Chris Grayling, has to exercise his powers to bring Oakwood into the public sector until it can get its management back on track."

However, Michael Spurr, chief executive officer of the National Offender Management Service said Oakwood had delivered "a safe, secure and ordered regime".

"The challenge of opening any new prison should not be underestimated," he added. "We will work with G4S and continue to monitor performance at Oakwood closely over the coming months."