LONDON (Reuters) - The British government has taken over the running of a major prison from contractor G4S after an inspection found that staff locked themselves in offices to avoid prisoners who were using drugs and violence with near impunity.

FILE PHOTO: Prison officers attend a meeting outside Birmingham prison in central England April 1, 2011. REUTERS/Darren Staples/File photo

The Ministry of Justice said on Monday it had taken back the running of HMP Birmingham for an initial six-month period to counter “squalid” conditions where blood, urine, vomit and faeces were left in cells, showers and corridors, attracting rats and cockroaches.

Inspectors to the prison said they were physically affected by the drugs in the atmosphere while their cars were set on fire during an arson attack.

Peter Clarke, Chief Inspector of Prisons for England and Wales, said he had not seen anything like it before.

“Think of squalor, filth, the air hanging heavy with the smell of drugs, the dilapidated physical environment, a sense of great instability, the feeling that at any time violence could break out.

“Put all that together, and what you have is a sense of an establishment that could not possibly fulfill any of the objectives of imprisonment,” he told BBC Radio.

The news is likely to revive the debate in Britain about whether private companies should be running core public services which came to a head earlier this year when Carillion, a contractor and outsourcing group, went bust.

Across England and Wales, there are 123 prison establishments, including youth offender institutes and other detention centers, of which 17 are run by private companies.

The Ministry of Justice said that in general contracted prisons are among the best performing across the prison estate.

G4S is the world’s biggest security company, employing 570,000 people in more than 90 countries.

But the company has had its problems over the years. It hit the headlines in 2012 when it failed to recruit enough security guards for the London Olympics, forcing the army to step in at the last minute.

In 2016, the government took over the management of a youth offending center in Kent from G4S and last year the company started an independent review into its Brook House immigration removal center after a BBC program showed staff behavior which G4S called “unacceptable”.

The Chief Inspector of Prisons said HMP Birmingham in Britain’s second biggest city had deteriorated dramatically in the last 18 months, with staff locking themselves in offices and prisoners openly using drugs.

It detailed one incident where a “clearly troubled man” who was struggling to maintain personal hygiene was drenched by prisoners who put a nearby fire hose through his observation panel.

“What we have seen at Birmingham is unacceptable and it has become clear that drastic action is required to bring about the improvements we require,” said Prisons Minister Rory Stewart.

The government said it would put in place a new governor, more staff and move around 300 prisoners to other sites.

G4S said the prison faced “exceptional challenges”. Its shares fell 2.6 percent in early trading.

“The well-being and safety of prisoners and prison staff is our key priority and we welcome the six month step-in and the opportunity to work with the Ministry of Justice to urgently address the issues faced at the prison,” the company said in a statement.