The Government has been urged to build more mental health facilities inside prisons after new figures showed more than 100 escapes from psychiatric hospitals last year.
At least 116 patients in medium and low-security psychiatric hospitals in England and Wales escaped from the institutions or from their escorting staff, according to figures obtained by the BBC.
Four patients remain at large. The figures compare to just five escapes from prisons and their escorting staff in 2007.
The former chief inspector of prisons, Sir David Ramsbotham, said the figures released by the BBC were "horrifying".
He told BBC Radio 4's Today programme: "It is a horrifying figure of course, but it's not one that surprises me because the medium and low-secure units in the NHS do not have the same degree of security a prison does."
He added: "The wake-up call is actually to the Government to build more facilities inside prisons because the public will know that those prisoners who have been sentenced for a crime and have mental health problems are being properly looked after inside what is essentially a secure place."
Professor Louis Appleby, national director for mental health in England, said comparing escapes with those from prisons was not a "reasonable comparison".
"There is a difference here between a prison and a secure unit - a secure unit is a hospital - the people who are in it are patients and they are ill," he said.
"If you give the impression that there are 100 people getting out and roaming the streets and threatening the public that is not an accurate impression about the risks that the mentally ill people present to the public."
