In a separate incident at the south London hospital, a mentally ill woman who was supposed to be under 24-hour supervision was allegedly raped by a fellow-patient, a convicted rapist. He had been moved after four years in high-security Broadmoor to a mixed psychiatric ward at Springfield Hospital, Tooting.
A member of staff was disciplined over the incident, which happened in December in a hospital kitchen and went unreported for many hours. The accused man was sent back to Broadmoor. The Crown Prosecution Service has decided not to charge him because of insufficient evidence.
The current police investigations involve allegations by five patients, some of whom have left the hospital. A seventh rape inquiry was recently discontinued for lack of evidence.
Last September, during a visit to the 400-bed Victorian hospital, Merton and Sutton Community Health Council, a watchdog group, criticised the ward where the alleged kitchen attack took place. It was particularly concerned at the practice of having patients with acute psychiatric problems staying on the same ward as mentally ill people convicted of crimes - known as forensic patients. These include people from Broadmoor.
Nathan Lee, chief officer of Merton and Sutton CHC, said yesterday: 'It's totally inappropriate to have people from high-security hospitals who may have committed very serious crimes with people who may have been sent to hospital for a few days with depression.' The ward involved has three beds for forensic patients out of 22.
The CHC is also worried that, in some of the wards, unlocked male and female dormitories are close to each other. Mr Lee described the hospital as a 'grim building' with little privacy and where women occasionally have to sleep in the same room as men.
The police have also expressed concern about the security at Springfield. Police and community health councils say sexual attacks on patients are a growing problem throughout the country.
Wandsworth Community Health Council, which also monitors Springfield, is calling for improved safety measures for women and seeking a meeting with the hospital managers. Helen Corrigan, chief officer of Wandsworth CHC, said: 'Staffing at the hospital is at the minimum safety level.' Staff are known to be unhappy at the number of agency nurses the hospital is forced to use.
The charity Mind is campaigning nationally for greater security for women in psychiatric hospitals and mental-health units. There is a fear that the police do not always take rape accusations from psychiatric patients seriously and that the Crown Prosecution Service is reluctant to prosecute people because it believes mentally ill patients make unconvincing and unreliable witnesses.
Dr Julie Hollyman, Unit General Manager at Springfield, said that three forensic beds would be moved to another ward following the rape allegation. 'We would not choose to mix forensic with non-forensic, but we do not have the facilities to keep them in separate wards - we are restricted by having to operate from a 19th-century hospital.
'It would be nice to have more staff - but we do bring in extra nurses when necessary.'