Vulnerable adults with learning disabilities could be left "isolated and stuck at home" when a day centre in Taunton is closed, the father of one of its users has said.
Six Acres is to shut by next April, as Somerset County Council is selling the site.
Mark Blaker, whose son uses the centre, has resigned from the board of service provider Discovery in protest.
The non-profit firm said plans were in place to provide new support.
Mr Blaker, from Wiveliscombe, said the centre was vital and he is angry at the way the council has handled the decision to sell it.
"A lot of people are unprepared for change and, for some of those people, predictability and stability are critical things in their lives," he said.
Discovery Somerset took over the learning disabilities service in April 2017.
Former employees previously told the BBC they felt standards were falling and there was a culture of fear.
The firm has also been criticised by families of adults with learning difficulties for not meeting their needs.
Luke Joy-Smith, the managing director of Discovery, said it was working with the council to change the way it offered support.
"Six Acres is in an isolated location and people with learning disabilities should be fully involved in their local community - which this change will facilitate," he said.
"Everyone will get the level of support they need, though in many cases that support will be different."
Discovery's centre at Bindon Road will also close, while the future of those living at Ashbury, Brambles and Oak is unclear.
Those at the residential centres will be invited to a meeting to discuss their future.