England's worst performing mental health trust has been rated inadequate for a third time, with patients trying to take their lives waiting for care.
Norfolk and Suffolk NHS Foundation Trust (NSFT) had unsafe acute wards and was seriously understaffed.
The Care Quality Commission (CQC) said bosses repeatedly failed to protect patients and a charity has called for the government to intervene.
Trust chief Antek Lejk said its culture needed to change.
Inspectors found patients left unsupervised in segregation, a high proportion of urgent referrals downgraded unsafely and that unfilled shifts led to 139 incidents in six months.
However, adolescent and child mental health wards were rated outstanding.
In its report, the watchdog said: "We saw many situations where people were not offered a service yet had been in significant need.
"Records showed that, in some cases, patients had self-harmed or taken overdoses whilst waiting for contact."
NSFT is the only mental health trust in the country to have been put into special measures, a step first taken in February 2015. The trust came out of special measures in October 2016, only to have that status imposed again a year later.
'Inadequate, poor and shocking'
Mearl Brown, from Cromer, Norfolk, sought help from the NSFT after his 19-year-old son Nyall first attempted to take his own life in January.
He said the care was disorganised and at one point the Brown family were advised to seek private medical help for their son.
Nyall went on to take his own life in May.
Mr Brown described the family's dealings with the trust as "inadequate, poor and shocking".
"The help wasn't given to him when he needed it," he said.
"He was in a bad way when he left hospital and we were sent home with a ticking time bomb.
"Local support would have been beneficial - one of the first assessments Nyall did was a telephone interview.
"I think the biggest problem is a lot of these places work Monday to Friday, 9 until 5 - mental health is 24-7."
Health Secretary Matt Hancock, who is also Conservative MP for West Suffolk, said "all options" would be looked at to improve the service.
"On the day of the publication of the report is not the time to make an immediate kneejerk response, but I am absolutely clear that we need to address it," he said.
"We need to absolutely get it right and I am going to do it.
"Since 1948, when the NHS was established, mental health trusts have been separate from the rest of the NHS and we have got to ask if that is the right solution.
"As the local MP, I have been working on this issue for many years and the service is not good enough and has serious problems."
Paul Farmer, from mental health charity Mind, said the options available to a health secretary included having parts of the service taken over by another mental health trust.
"When a trust fails and then fails again, you have to ask questions about what action needs to be taken to change that."
The CQC's lead for mental health, Dr Paul Lelliott, said: "Managers have not ensured that when things go wrong, they learn and share lessons to reduce the likelihood of the same thing happening again."
He said issues first raised in 2014 had still not been fully addressed.
"The trust leadership team has not taken action at the pace required to bring about sustained improvement and to resolve failings in safety," he said.
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The inspection body said it had asked NHS Improvement to support the trust to make immediate changes to keep patients safe, and would be monitoring.
NSFT was rated inadequate in the areas of safety, management and response.
It required improvement over the effectiveness of its services but was found to be good at being compassionate in its care for patients.
Antek Lejk, the trust's chief executive, said: "It is not a clinically-led organisation.
"We don't give power to our doctors and nurses to change things and make the decisions they need to do and we are going to change that.
"We are looking at creating new clinical leadership roles in the organisation."
Mr Lejk, who took over in May, said it was also working with "one of the best mental health trusts in the country" - the East London NHS Foundation Trust - to make improvements.
He added 100 staff would be trained in a "quality improvement initiative" and would then go back on to wards and teams.
"Our priorities now will be to resolve ongoing issues around access to services, waiting lists, care planning and staffing levels, while also making sure we have the right systems in place to ensure patient safety at all times."
Clive Lewis, Labour MP for Norwich South, said: "This has become a national disgrace. We are looking at a national and local system-wide failure of governance, commissioning, regulation and inspection," he said.
"Unless we change course, I know exactly what's coming next. Senior trust board members will mouth the same platitudes about lessons being learnt and plans for change - even though those same people have long track records of failure in various parts of the local NHS."
Mr Lewis said the CQC had "the power to put the trust into Special Administration and get rid of this board".
North Norfolk Lib Dem MP Norman Lamb, who was a health minister in the coalition government, said it was "totally intolerable for families and individuals affected".
In a statement, the Department of Health and Social Care said: "NHS Improvement is providing intensive support to Norfolk and Suffolk NHS Foundation Trust to improve patient safety and deliver sustainable improvements. The situation is being monitored closely and we expect to see progress made in the coming weeks."
Following the report, trade union Unison said staff were "working hard to do their best by patients despite low morale and ever-dwindling resources".
Regional organiser Peter Passingham said it was "not surprising that the trust has failed to improve since its last inspection" given "the wounds inflicted by nearly a decade of austerity."
By Sophie Hutchinson, BBC News Health Correspondent
Today's report by the Care Quality Commission catalogues a mountain of failings.
It says significant concerns raised back in 2014 had still not been addressed and that in some cases the trust had created new risks.
This is the third inspection in three years that the trust has failed and it is in unprecedented territory as the only mental health trust to have been placed in special measures.
Now there are calls for radical and urgent action and for it to be placed in special administration.
That's the NHS's so-called failure regime in which some parts of the trust or all of the trust are taken over.
It would require the intervention of the health secretary. It's a measure of last resort only used twice before, but many mental health experts and local campaigners feel it is the only way to make these services safe.