More than 800 vulnerable mental health patients in Norfolk have not been assigned care workers due to staffing shortages, a report has revealed.
The 839 unallocated cases at Norfolk and Suffolk NHS Foundation Trust include 139 youth team cases.
The trust, now in special measures, is looking to employ more care workers.
It said "unallocated" patients were better described as "on waiting lists" and that emergency cases were seen in four hours.
Unison said services at the trust had been "savagely cut".
A trust report, to be discussed at a board meeting on Thursday, said there were no equivalent figures for Suffolk figures but states "it is known" they were "much lower than in Norfolk".
The report said the trust - which last week became the first of its type in England to be put into special measures - was looking to employ extra care co-ordinators to reduce the number of unallocated cases.
The report identified 683 cases unallocated in December 2014.
It said the trust was taking a number of actions to "reduce the number of unallocated cases and to mitigate the risks inherent in the unallocated cases".
It added: "This includes the identification of an additional 12 care co-ordinator posts."
Scarlett Mellors, of Norfolk, had a breakdown after having family problems and was diagnosed with severe depression.
She battled for 18 months to get a new care co-ordinator after her old one went on long-term sick leave.
Ms Mellors said it was "extremely isolating" as she did not know who she was supposed to go to.
After complaining, she finally got a new care co-ordinator and said: "It transformed my life".
That care co-ordinator is now helping her to claim benefits and sort out her finances.
Rebecca Edmunds, 25, of Beccles, Suffolk, was diagnosed with Obsessive Compulsive Disorder at the age of seven and also suffers from anorexia.
Ms Edmunds said: "My care co-ordinator has been invaluable." She now has the confidence to do work for BEAT (an eating disorder charity).
Debbie White, the trust's director of operations, said an "unallocated case" did not mean an individual could not access appropriate services while waiting to be allocated a care co-ordinator,
"It is regrettable patients have to wait but we have implemented a number of measures to ensure they have regular contact," she said.
"They will receive a letter at the time of referral with the duty worker phone number clearly documented and, should circumstances change, they can call the team where support will be provided.
"Each clinical team now has a daily duty worker for patients who may require additional support in the absence of an allocated worker."
Emma Corlett, of Unison, said: "When I saw the number who had not been allocated a mental health worker I was really shocked.
"This has happened because services have been savagely cut. There are not enough enough staff to meet the needs of the service."
A spokesman for the Campaign to Save Mental Health Services in Norfolk and Suffolk said: "A named care co-ordinator is a key element in providing a safe, proactive service and continuity of care. It is astonishing that this crisis has been allowed to develop."