Eleven (16%) of 69 NHS mental health trusts provide “weak” inpatient care, according to a review by the Healthcare Commission.

Thirty mental health trusts (43%) provide a "fair" service, while just eight (12%) are “excellent”, and 20 (29%) “good”

Of the 15 mental health foundation trusts, 10 (66%) were either good or excellent, and five (33%) were fair. None were weak.

The commission's review of NHS acute adult psychiatric inpatient services covered 554 wards providing almost 10,000 beds for patients aged between 18 and 65.

The watchdog used performance data and patient and staff surveys to judge trusts on four key criteria - standard of care, involvement of patients and carers, safety, and a patient's journey through the system.

Over recent years a number of reports have revealed that NHS psychiatric units are often unsafe and untherapeutic.

In its review, commissioners again highlighted the high levels of violence, with 45% of nurses and 15% of patients reporting that they were physically assaulted in 2007.

Last month, the Royal College of Psychiatrist’s new president, Professor Dinesh Bhugra, said many inpatient units are so unsafe, underfunded and overcrowded that he would not use them. "And neither would I let any of my relatives do so," he added

Initiatives, including a voluntary psychiatric ward accreditation scheme by the Royal College of Psychiatrists, are trying to drive up standards.

Prof Bhugra wants the government to introduce a compulsory system of accreditation for all acute, inpatient psychiatric wards.

"Until there is a compulsory scheme, my prediction is that, as overcrowding increases, funding becomes more stretched and morale of patients and staff fall, overall conditions are likely to continue to deteriorate,” he said.

In its report, the commission also raised concerns that, in a six-month period, patients detained under the Mental Health Act 1983 were absent from services without authorisation on 2,745 occasions.

The report, entitled The Pathway To Recovery, also concluded that better co-ordination is needed to ensure that service users do not spend any longer in hospital than necessary and are supported when they move from hospital to community services.

Professor Louis Appleby, the government's national director for mental health, said more government money was being invested to address the range of problems.

"We have not waited for this report to take action on the issues raised," he said.

"For example, £130m has been allocated over the last two years alone to improve environments and promote safety on acute wards."

Emily Wooster, policy officer at Mind, said: "The best performing trusts were those that provided a therapeutic environment and engaged patients in meaningful activities - these things shouldn't be the preserve of our best hospitals, but should be absolutely fundamental to mental health care across the board.

"And yet again, we are confronted with more evidence that some mental health wards can be hostile and unsafe. No one should be expected to tolerate being housed in an environment where they feel threatened and at risk."

The Royal College of Psychiatrists this month launched its "Fair Deal" campaign which, over three years, will push for more mental health research funding, continued increases in public expenditure on mental health, and the development of long-term funding strategies for mental health service provision.