The loss of learning disability specialists could lead to a return to Victorian-style care, leading nurses have warned.
The number of learning disability nurses in England dropped by 40% from 5,368 in May 2010 to 3,247 in April 2018, figures from NHS Digital show.
Many patients may end up being cared for away from their friends and family without enough specialist support as a result, the Royal College of Nursing (RCN) said.
Dame Donna Kinnair (pictured), director of nursing, policy and practice at the RCN, said: "The nursing shortage in England is harming some of the most vulnerable members of society.
"Those with learning disabilities already face a lower life expectancy and poorer health outcomes than the general population, and a lack of specialist knowledge will make matters worse.
"Without the specialist support provided by registered nurses, more patients may end up in institutions, away from their families and friends and shut off from society.
"This bleak Victorian image is not what care should look like in the 21st century."
There was a 40% drop in the number of students aged over 25 applying for nursing courses between 2016 and 2018, Ucas figures show.
The fall is particularly concerning because mature students are more likely to study learning disability and mental health nursing, the RCN said.
Meanwhile, a survey by the Council of Deans for Health on behalf of Health Education England (HEE) carried out in May found around half (46%) of universities in England have discussed discontinuing learning disability nursing programmes in September.
Dame Donna said: "Ministers have known about the steady drop in applications for the best part of a decade, and have allowed a crisis to develop in learning disability care.
"We want to see urgent investment to attract more applicants into learning disability nursing, and an effective workforce plan to ensure every member of our society receives safe and effective care."
Learning disability nurses provide specialist care in the community and in some acute trusts.
Justin Madders, Labour's shadow health minister, said the warning "must serve as an urgent wake-up call".
"Under this Government learning disability nurses have been cut to the bone, and they appear to have gone quiet on their plans to attract more students into the profession," he said.
"This unprecedented workforce crisis is completely unacceptable."
A Department of Health and Social Care spokeswoman said: "We're committed to ensuring people with learning disabilities receive high quality care and we are looking at how we can recruit more nurses into specialisms such as learning disabilities, including an accelerated post-graduate programme.
"While there are now record numbers working in the NHS, investing in our workforce will continue to be a top priority and we recently announced the biggest ever increase in training places for nurses, doctors and midwives."
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