A North Yorkshire MP has said she "deplores" the decision to close a ward at Malton Hospital by Friday.
The Ryedale ward, which has recently undergone a £1m refurbishment, is being shut as part of plans to treat more patients in the community.
Thirsk and Malton Conservative MP Anne McIntosh MP said she was concerned for the future of the hospital.
North Yorkshire County Council's health committee is also writing to the health secretary over the plans.
Miss McIntosh said: "I wholeheartedly deplore the announcement that Ryedale ward will be closed by the end of the week."
She added that she was "now deeply concerned for the future of the whole of Malton Hospital".
"Ryedale ward has been closed without prior consultation of the local health practitioners and I now fear that the whole hospital may suffer the same fate."
The 22-bed ward reopened six months ago after a £1m refurbishment, £250,000 of which was donated by the hospital's League of Friends.
NHS North Yorkshire and York said the changes were part of a pilot scheme which would be evaluated next March and if adopted permanently, would be put out to public consultation.
Janet Probert, managing director of North Yorkshire and York Community Mental Health Services, said: "We are fully aware of the local concerns about our enhanced community services pilot scheme and we are working with a range of people to make sure we understand and allay those concerns.
"This important pilot is part of our wider plan to reduce the number of unnecessary hospital admissions, enable quicker discharge from hospital and establish better follow up care for people who do require a hospital admission."