Sexual incidents are "commonplace" on mental health wards, a new report suggests.
Patients and staff have been left distressed after receiving unwanted advances and being spoken to in a sexualised manner, the Care Quality Commission (CQC) said.
The regulator is calling for new national guidance to improve safety on mental health wards.
The CQC analysed reports to the NHS National Reporting and Learning System by 54 mental health trusts in England between April and June last year.
It found 1,120 sexual incidents involving patients, staff and visitors - around 40% of which could be described as sexual assault or harassment, the CQC said.
Among the total, there were 298 incidents of nudity or exposure, 273 of alleged sexual assault, 242 of verbal abuse using sexual words and around 29 of alleged rape.
The majority (95%) of reported incidents on mental health wards were said to have been carried out by a patient.
The analysis follows a report by the regulator last year, which described mental health wards as a "high-risk environment" and raised concerns about the number of violent incidents involving staff and patients.
Dr Paul Lelliott (pictured), deputy chief inspector of hospitals at the CQC, said: "This report published today shows that sexual incidents are also commonplace on mental health wards and can cause great distress to those affected, distress that may still be felt long after they leave hospital."
People who have used services "described the distress they experience when other patients speak to them using sexualised language or when they observe other patients behave in a sexually disinhibited manner due to their mental ill health", the report said.
It added: "Some told us that they had received unwanted sexual advances from other people or that they have engaged in sexual acts when mentally unwell that they have regretted afterwards.
"This distress is still very real for people after they leave hospital.
"We would not wish for this work to have an impact on safe and fulfilling sexual relationships, as they are a part of a person's human rights.
"But as the quality regulator, our priority is to ensure that people using health and care services are kept safe, that due consideration is given to their mental capacity and that their privacy and dignity are maintained."
The CQC said it will work with NHS Improvement, NHS England and the Royal College of Psychiatrists to improve the safety of those on mental health wards.
Dr Lelliott said: "Patients and staff must feel confident that any concerns will be followed up quickly and effectively and the appropriate action taken.
"We are recommending new national guidance co-produced with people who use services, a strengthening of the reporting system so that it better reflects the impact of sexual incidents, and training to equip staff with the skills and knowledge to fully assess patient risk to help prevent incidents.
"Staff on mental health wards must work together with the police and local authority safeguarding teams to help ensure that people accessing mental health services are kept safe from sexual harm at what is a very vulnerable time in their lives."
Dr Adrian James, registrar of the Royal College of Psychiatrists, said: "Sexual safety is of paramount importance for those providing and receiving treatment, and while the overwhelming majority of patients receive care in a safe environment, the report highlights that more needs to be done.
"The College is committed to working with the CQC and other agencies on taking the recommendations forward to ensure excellent and safe patient care."
Copyright (c) Press Association Ltd. 2018, All Rights Reserved. Picture (c) CQC / Youtube.