England's director of mental health care today called for tougher standards for secure hospitals after it emerged that at least 116 mentally ill criminals escaped last year, more than 20 times the rate of escapes by offenders held in prison.

The information, which was only brought to light after a Freedom of Information request, has cast doubts over whether security is adequate at psychiatric units housing offenders who may pose a risk to the public.

Yesterday, mentally ill childkiller Darren Harkin was sentenced to be detained indefinitely at Broadmoor Hospital after he escaped from a secure private hospital near Bristol and raped a 14-year-old girl at knifepoint. The judge who sentenced him criticised the regime at Hayes Hospital, which had failed to pick up on the 21-year-old's increasingly disturbed behaviour.

The National Autistic Society, which runs Hayes Hospital, has set up an independent inquiry into the case, and is due to report by the end of the month.

Professor Louis Appleby, England's national director for mental health, told BBC Radio 4's Today programme that in the wake of the Harkin case it was time for the government to consider intervening to set national standards for medium and low secure units.

"The inquiry will tell us a bit more about what has happened in that particular unit, but meantime we well be looking to see that high risk individuals are not placed there," said Dr Appleby.

"The issue of security is something that has evolved in the Health Service. There isn't a very good definition of what a low secure unit is for, and what its standards are. I think we now need to set national standards, we can't just allow things to continue to evolve."

In January 2000 Harkin, aged 12, had walked into a police station in Bristol and confessed to the murder of his stepbrother. He had stabbed the baby in the head and chest with a kitchen knife and cut off his right arm.

Harkin could give no explanation for his actions, and doctors later diagnosed schizophrenia and “autistic spectrum disorder”, which meant that he was unable to comprehend the consequences of his actions on other people. He spent several years in a medium-security psychiatric hospital before being transferred to the Hayes in the village of Pilning near Bristol. There Harkin was allowed to make supervised visits to the cinema and local snooker clubs despite a history of running away.

In February Harkin absconded but the supervisor did not raise the alarm for half an hour for fear of “panicking” other residents.

After his escape, Harkin burgled a nearby house before crossing the Severn Bridge on foot and abducting a 14-year-old schoolgirl at knifepoint in Chepstow high street. He threatened to kill the girl before raping her twice. After his arrest it emerged that Gwent Police had not been alerted about his escape.

Leighton Hughes, for the prosecution, told the hearing at Reading Crown Court that Harkin's behaviour had got worse in the time before his escape and that he was supposed to be on 24-hour watch. On one occasion he had asked a woman staff member for sex and when she said “no”, asked if there was anyone else available.

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