Mental health patients sent away from home for treatment have travelled the equivalent of 22 times around the world in a year.
Patients were forced to travel 555,000 miles in a year because there were no locally available beds, the Royal College of Psychiatrists (RCPsych) said.
The College estimated the figure by analysing NHS data on a range of distances travelled by patients subject to 8,640 inappropriate placements active between August 2018 and July 2019.
Out-of-area placements can have a devastating impact on patients and their loved ones, can set back recovery and be challenging for staff, the College said.
They are deemed inappropriate when a patient is sent out-of-area because no bed is available for them locally, and represent the vast majority of all out-of-area placements.
Allowances are made when a patient requires highly specialist care.
While the Government has pledged to end all inappropriate out-of-area placements by 2021, the College said progress to meet this target has stalled.
On July 31 this year there were 745 people were being treated inappropriately out-of-area, according to official figures.
RCPsych president Professor Wendy Burn said sending patients far away from their support systems was a “shameful practice”, and that cuts to the number of beds had gone “too far”.
She said: “Trusts struggling with dangerously high levels of bed occupancy are being forced to send seriously ill people hundreds of miles away from their homes for care. That must stop.
“Beds are being closed to move resources to the community so that people can be treated close to friends and family and without having to leave their homes.
“The RCPsych agrees with that principle. But the reality in many areas is that beds have been lost and investment in community services is only now starting.
“As a result, precisely the opposite effect has been achieved with some severely ill patients sent hundreds of miles for care.”
Since 1987/88 the number of mental health beds in England have fallen by 73% from around 67,100 to 18,400.
Overall occupancy currently exceeds 90%. The College recommends levels do not exceed 85%.
A report commissioned by the College estimates that a further 1,060 beds are needed to reduce these to an acceptable level.
But even if extra beds were made available, substantial or immediate improvements in occupancy rates are unlikely given existing pressures, the research said.
The report, Exploring Mental Health Inpatient Capacity, identified 13 areas that are particularly struggling.
The areas with high levels of inappropriate out-of-area placements are: Bristol; North Somerset and South Gloucestershire; Devon; Lincolnshire; Norfolk and Waveney; Nottinghamshire; Lancashire and South Cumbria; and Hampshire and the Isle of Wight.
Added to this, the areas where mental health bed occupancy rates regularly exceed 95% are: Devon; Birmingham and Solihull; Cornwall, Mid and South Essex; North Central London; South East London; and Sussex and East Surrey.
Vicki Nash, head of policy and campaigns at Mind, the mental health charity, said it is “tantamount to negligence that beds are being cut in some areas without a viable alternative”.
She said: “The NHS promised to completely eliminate inappropriate out-of-area placements by 2021 and yet as recently as July hundreds of people were still being sent hundreds of miles from their home to receive care.
“This can worsen people’s chances of recovery, increase their risk of suicide and have a devastating impact on family and friends.
She added: “Commissioners must do whatever it takes to ensure people get the right care, in the right place, at the right time – whether that’s an inpatient bed or support in their community.”
Saffron Cordery, deputy chief executive of NHS Providers, said: ““The report rightly highlights that there are a complex range of factors behind people being placed in services far from home and these placements are often a symptom of pressures on the wider system more broadly.
“We need to see the right investment in community services, housing, social care and workforce, as well as broader approaches to reducing demand to be in place and working. It is also important that the right types of services are commissioned and trusts have the flexibility and right level of capacity and resource to deliver these.”