More than 100 patients have gone missing from mental health hospitals at the North East London NHS Foundation Trust in the past two years.
The trust provides mental health services for people living in Barking and Dagenham, Havering and Redbridge.
Mental health charity Sane said it was increasingly concerned at the number of patients absconding from facilities, and blamed years of "relentless cuts" for creating appalling conditions on wards.
NHS figures show that 135 patients who had been sectioned under the Mental Health Act went Awol - absent without leave - from North East London NHS Foundation Trust between April 2017 and March 2019.
A patient is deemed Awol if they leave the hospital they are detained in without permission, or fail to return after being allowed out on temporary leave.
Marjorie Wallace, chief executive of 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."
A spokesman for NELFT said: "We are constantly striving to improve our safety culture and the security of our sites. Last year additional fencing was put in place, which has proven beneficial to the security of our site.
"Initiatives that include our safe wards programme, improved working relationships with the police - through our bi-monthly liaison group with all involved agencies and monitoring our care planning and risk assessments - these are all steps NELFT has put in place to assist with patient safety.
"By proactively managing our patients who may be an absconsion risk, care planning and planning of leave, we are able to minimalize potential risk.
"Our approaches all point towards improved care and management of risk."
An NHS spokesman said an extra £2.3billion was being invested in mental health services as part of the NHS Long Term Plan and the money will go towards making sure inpatient facilities are properly resourced.
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