Steven Carr, 31, who has autism and learning disabilities, has had full-time support workers with him since he was 18 years old.
And they say Steven, who has also been diagnosed with a personality disorder, has been left frightened and alone as he is put to bed each night and locked in until the morning.
Mum Mollie, of Tranent, said: “A few months ago we were told they were going to try Steven on one or two nights on his own as they thought he could handle it.
“The first Saturday night he stayed with me after it was introduced I found him huddled in his bed under blanket after blanket.
“When I asked what he was doing he said it was what he did when he was left, he said ‘I hear the door lock and I hide under all the blankets until the morning’. I was heartbroken.”
East Lothian Health and Social Care Partnership, which oversees the care service, confirmed it has been reviewing overnight support but insisted it is only making changes to people who could “safely sustain that change”.
Despite their concerns about Steven’s ability to cope, Mollie and her ex-husband David were told their son’s overnight support was stopping completely last week.
In its place is a community alarm but David and Mollie say Steven has expressed fears about using the button and they do not believe he would use it even in an emergency.
And while a key is left in the property to open the door from the inside, they say Steven’s learning disabilities are such that he cannot use it.
Mollie said: “Steven is scared of the red button. We don’t believe he would be able to use it in an emergency.
“If a fire broke out or someone was trying to break in he would not be able to cope or respond, it is extremely worrying for us and for Steven.
“He is just locked up like an animal and left overnight. It is cruel and is clearly having a detrimental effect on him.”
Dad David is calling for a full medical and psychological assessment of his son’s ability to be left overnight to be carried out.
He said: “This is not about care, it is about saving money. It is a huge step back if it means simply locking people in their homes at night.”
A spokesperson for the health and social care partnership said: “We cannot comment on individual cases but we would like to assure readers that any decision to move someone to different provision is only taken after full discussion with the service-user and professionals (and carers, where possible) and when we are confident that the service-user could safely sustain that change.
We have been working with service-users and carers to look at other means of support over the 24-hour period, more suited to the service-user’s own wishes.”