Questions raised over safety of vulnerable inmates in outsized jails and scope for cost savings

A prisons watchdog has cast doubts on the UK government's proposed programme to build three huge, “Titan” jails, saying they could be dangerous for vulnerable inmates and that ministers had failed to show how the scheme would save money.

The super-sized jails, which would each hold up to 2,500 prisoners, have been proposed as part of a drive to ease overcrowding. The Ministry of Justice is searching for sites of at least 20ha for the buildings.

But the National Council of Independent Monitoring Boards has said it has “fundamental doubts” about the idea and that ministers are ignoring key concerns about monitoring conditions in prisons.

In its response to a government consultation on the issue, the council said: “There will be major and potentially dangerous consequences if services such as health and education are provided centrally, as it will be difficult to protect the most vulnerable prisoners from those who might cause them harm.”

Construction of the Titan prisons would cost an estimated £350m each. The most likely spots for them are thought to be in London, the West Midlands and the North-west.