NHS figures show 3,462 mental health patients went AWOL from facilities between April 2018 and March 2019.
Thousands of patients went missing from mental health hospitals in England last year, NHS figures show.
A total of 3,462 people who had been sectioned under the Mental Health Act went AWOL – absent without leave – from facilities between April 2018 and March 2019.
This is a 4.4% rise on the previous year during which 3,316 patients went missing.
A patient is defined as AWOL if they leave a treatment centre without permission, or fail to return after being allowed out on temporary leave.
Greater Manchester Mental Health NHS Foundation Trust recorded the highest number of missing patients, with 625 incidents.
It was followed by the Birmingham and Solihull Mental Health NHS Foundation Trust, with 190.
Marjorie Wallace, chief executive of mental health charity SANE, said: “We are increasingly concerned at the number of patients across the country that go missing for one reason or another, particularly those who become acutely ill without their medication and who can become a risk to themselves and others.
“We need urgent action to prevent patients going absent, or we risk an increase in suicides amongst this group.”
Alison Cobb, specialist policy adviser at the charity Mind, said: “Mental health services have a responsibility to ensure the safety of those in their care and any failings, including people absconding, should be thoroughly investigated.”
An NHS spokesman said an extra £2.3bn was being invested in mental health services as part of the NHS Long Term Plan.
The money will go towards making sure inpatient facilities are properly resourced as well as early interventions for patients to prevent problems escalating, he said.
He added: “The government is rightly reviewing the Mental Health Act to protect some of the most vulnerable people in our society.”
The figures come eight weeks after the government pledged to review all cases of segregation following a review by hospital regulator the Care Quality Commission, and a highly critical report by the children’s commissioner for England.