Black patients in Devon were more than four times as likely as white patients to be detained under the Mental Health Act last year, new figures show.
The Race Equality Foundation said inequality in mental health detentions across England is "not new or surprising" due to a failure to invest in early intervention and preventative measures.
Under the Mental Health Act, people with a mental disorder may be formally detained in hospital – or 'sectioned' – in the interests of their own health or safety, or for the protection of other people.
NHS England figures show about 750 white patients were detained under the Act in NHS Devon Integrated Care Board the year to March 2022, while just 15 patients detained were black or black British.
However, the rate of detentions when taking population size into account was higher for black patients in the area at289 per 100,000 people compared to 65 per 100,000 for those that identified as white.
It meant black patients were 4.4 times as likely to be subject to a mental health detention in 2021-22.
She said: "The real question is why has this not changed despite being well documented over a number of years not just with these new figures? The health and care system fails to invest in early intervention even though this has been highlighted as an issue for a long time."
She said nothing will change unless inequality in care is taken seriously.
"A failure to invest in early intervention and preventative measures means that problems are allowed to develop until things reach crisis point," she added.
Nationally, 53,337 new detentions under the Mental Health Act were recorded in 2021-22. Yet, the overall totals will be higher as not all providers submitted data and some submitted incomplete data.
Amongst the five broad ethnic groups, the rate of detention for black or black British people (342 detentions per 100,000 population) was nearly five times that of white people (72 per 100,000 population). It meant they were the most likely ethnicity to be detained.
An NHS spokesperson said the health service is committed to fighting health inequalities.
They added the launch of a dedicated Advancing Mental Health Equalities Strategy in 2020 has ensured steps to improve the access, experience, and outcomes for people from ethnic minority groups who need mental health care.
They said: "The NHS has also launched a new quality programme to ensure hospitals are supporting people who are detained under the Mental Health Act, including addressing inequalities in how the Mental Health Act is applied."