Almost 30 fires were started by mental health patients in psychiatric units across Lancashire last year.
The trust that runs the centres, including The Harbour in Marton, disclosed the figures under freedom of information laws.
It said nobody has faced prosecuted.
Lancashire Care said there were 29 arson attacks recorded in 2016/17, with 28 believed to have been started by patients.
All happened in ‘in-patient areas’ such as bedrooms.
Firefighters were called to Blackpool’s flagship mental health facility, in Preston New Road, last month after a patient started a blaze in their room – though the fire was out by the time they arrived.
A spokesman for Lancashire Care said: “The safety of our patients, staff and visitors is our number one priority at all times, and we have robust procedures in place to manage fire safety.
“As a Trust, we go above and beyond to meet fire safety standards. For example, our facilities are fitted with ultra-sensitive smoke detectors and, because of their sensitive nature, the overwhelming majority of times that fire alarms have gone off have been accidental and caused by things like steam from showers or cooking.
“Deliberate fires have been very small and few, and mainly involved toilet paper being burnt. None of the fires over the time period caused any injuries and were dealt with in a timely manner.”
In November, Heather Loveridge’s inquest heard how the mother-of-four died after setting herself on fire with a cigarette lighter she had in her handbag.
Mrs Loveridge, 56, who had psychotic depression, was a voluntary patient at the Cavell Centre in Peterborough, the BBC reported, and died two days later on August 19, 2016.
The hearing was told her handbag had not been searched – despite lighters being banned from the wards on the unit, run by Cambridgeshire and Peterborough NHS Foundation Trust.
Medical director Dr Chess Denman later apologised to Mrs Loveridge’s family and friends, and said an investigation had led to the trust ‘strengthening our processes around searching patients’ belongings’.
A spokesman for Lancashire Fire and Rescue Service said the fires had ‘mercifully not led to any major incidents’, and added: “At the same time there’s no complacency and we work with institutions to make sure events like that don’t happen where possible.”