An inpatient at a secure psychiatric hospital allegedly smuggled drugs onto his ward and shared them with others - leading to "incidents" including an assault.
The man, who was staying at the low-security Rathbone Hospital on Mill Lane, Old Swan, is believed to have "secreted the drugs on his person" after being allowed to temporarily leave the unit.
Managers at Mersey Care NHS Foundation Trust, which runs Rathbone, said the issues had led to a spike in incidents in May this year.
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A safety report to the trust's board of governors, referring to the incident, said the service user "bringing illicit substances onto the Unit for himself and peers" resulted in subsequent incidents including a patient on patient assault.
The report said: "The last two incidents of illicit substances being brought onto the Unit, has involved the same service user and the distribution of drugs to others, and the service user’s placement on the Unit is being reviewed.
"Patients are aware they will be searched on their return to the ward and are secreting the items within their person.
"Owing to the layout of the ward it's difficult to monitor all patients’ activities and its been recommended that consideration be given to use of CCTV on the Unit."
The type of drug taken onto the ward and whether any injuries were caused during the assault was not clear.
Mersey Care NHS Foundation Trust said an "internal learning review" was underway after the incident.
A spokesman told the ECHO : “Our clinical teams place an emphasis on patients in low secure services accessing the local community as part of their rehabilitation programmes, including staged processes before they are ready to be granted unescorted leaves of absence.
“Security measures are in place to prevent patients returning with illicit substances and incidents of substance misuse remain extremely low.
"When drugs are found, nurses follow clinical guidance to assess patients’ mental and physical health and access additional support services if required.
“Mersey Care remains committed to providing the highest standards of care to keep our patients, service users and carers safe and delivering an environment that helps their individual rehabilitation programmes.
"We are prevented from discussing individual patients because of rules governing patient confidentiality.”
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