More than 300 patients have gone missing from mental health hospitals run by the East London NHS Foundation Trust (ELFT) in the past two years.
NHS figures show 365 patients sectioned under the Mental Health Act went absent without leave (Awol) from ELFT between April 2017 and March 2019.
The trust provides mental health services for boroughs including Newham and Tower Hamlets.
Patients are deemed Awol if they leave without permission or fail to return after being on temporary leave.
Across England, the number of incidents increased by more than 4per cent over the two years, from 3,316 in 2017/18 to 3,462 in 2018/19.
Mental health charity Sane blamed the increasing number of patients going absent across England on years of cuts, creating poor conditions on wards.
Marjorie Wallace, chief executive of Sane, said absences among sectioned patients could lead to an increased risk of suicide.
"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," she said.
In England, 11 patients died whilst Awol over the two-year period.
Alison Cobb, specialist policy adviser at the charity Mind, said it was difficult to draw definitive conclusions from the figures.
But she said the Mental Health Act is used in a way that fails to treat people with dignity and respect.
"Hospital wards can be stark and inhospitable, and when people are sectioned they are sometimes subject to unnecessary restrictions and practices such as physical restraint, seclusion or forced medication," she said.
An NHS spokesman said £2.3billion was being invested in mental health services in the NHS Long Term Plan.
An ELFT spokesman said it takes safety very seriously, with patients being permitted to leave their wards - after a risk assessment each time - as part of their rehabilitation.
This is to help patients develop confidence and independence, but isn't done if they've been arrested or charged by the police.
"The majority of people who are reported as absent have been on a period of leave from hospital as part of their recovery and return at a later time than planned," he added.
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