The chief inspector of prisons has issued a damning verdict on the conditions in Brixton prison - criticising both the prison service and ministers for allowing the jail to slide into an abject state of neglect.

On Wednesday Sir David Ramsbotham said staff at the jail had let conditions decline for four years, adding that the prison had been failed by government and senior staff who had provided insufficient funding and poor management

His report, published on Wednesday, singled out the healthcare centre, which houses 66 patients, for criticism. It lists a catalogue of filth and neglect with dirty mattresses, broken furniture and unclean toilets.

Staff in the centre are also criticised for falsified paperwork about the times at which they monitored prisoners at risk of suicide. Sir David describes their actions as "despicable".

He says: "If the prison service lets staff get away with such appalling irresponsibility, in such an important area involving the saving of human life, it should not be surprised if people suspect that it is being indigent in its supervision of many other aspects of the treatment of prisoners. This report reveals inefficiencies, inappropriateness and irregularities which should not have been allowed to happen."

He blames those across the service and in all areas of the prison. "Management at all levels is guilty of condoning existing malpractice or not knowing it was going on," he said.

Head of the prison service, Martin Narey has defended the jail. "We acknowledged that there were fundamental problems and the management at Brixton was not as effective as it needed to be. There is a great deal more work to be done at Brixton. However, I am confident that the new management team will rejuvenate the culture and morale at the prison," he said.

The Howard League for penal reform said the report was an accurate reflection of the Brixton regime. "A lot of the findings were expected. There are very serious deficits in what the prison provides. There are no workshops and there is no space to build. A gym has been built outside the prison walls but only low category prisoners can use it," said Tim Colborne.

But he added that things were changing: "The majority of staff are doing a difficult job in difficult circumstances and things have moved on since the report was written. The prison's physical state is better but staff morale is very low. Relentless criticism doesn't help. Essentially the service neglected Brixton. There is a line-management issue. A lot of people knew what was going on but chose to ignore it."

The central problem is not the management of the prison, says the Howard League, it is simply the age of the jail compounded by decades of neglect. "The threat of privatisation has been making things change. That's not to say that privatisation will provide a better level of service. The prison is now over 160 years old and was not designed for the number of offenders that now has. The long-term aim should be to close places like Brixton," said Colborne.