Shropshire Community Health NHS Trust announced earlier this month that it would be "temporarily closed on safety grounds".
The trust, which manages the 16-bed hospital, said staffing issues over the last six months had left it "extremely difficult" to run the hospital.
Officials said patients would be assessed and discharged to "the appropriate place of care" by the end of Sunday.
But the Shropshire, Telford & Wrekin Defend Our NHS group has written to the trust's chief executive Patricia Davies to say bosses need to think again.
Campaigners have accused the trust of making the decision on costs grounds, and fear that the closure could become permanent.
The letter, which has been signed by the group's chairwoman Gill George and secretary, Councillor Julia Evans, says: "The trust has given no information to suggest an active recruitment plan; it has set no criteria for reopening; it has given no timescale for reopening; nor has it explained the need to close the whole hospital: inpatient beds and a range of outpatient services.
"With no plan for the hospital to reopen, it is of course unlikely that it will reopen. Temporary will simply drift into permanent."
The group says the closure comes as the NHS already faces unprecedented pressures and 'unacceptable' ambulance response times.
The letter states: "The reality is that people are already dying avoidably.
"There are multiple strands in this situation. These include GP services that are under enormous pressure and community services that are struggling. Crucially, though, there is a shortage of beds.
"The NHS probably now faces the worst winter in its history.
"There will be a desperate, desperate shortage of beds – in Shropshire and across the UK – in the coming months. Shropshire needs every bed it can get. This includes community hospital beds.
"To take 12 to 16 beds out of the system, at the start of a period when every bed is desperately needed, is genuinely a perverse decision. This will cost lives."
The group says the trust also has a duty to involve patients and the public in the development and consideration of proposals for changes in the way services are provided.
"We are not aware of prior discussion with staff or trade unions," the letter adds.
"There was no attempt to involve service users or the wider public."
Last week, Ludlow MP Philip Dunne raised the issue of the temporary closure in the House of Commons.
In a question to health minister Edward Argar, Mr Dunne asked: "Will he work with me to put pressure on the local NHS to develop a plan to recruit suitably qualified nurses and reopen the hospital as soon as possible?"
Mr Argar agreed with the importance of community hospitals and added: "I am grateful to him for drawing that to my attention and I will look into the specific situation he raised.
"It is important that, alongside providing a service, it is a safe service.
"I am happy to work with him to see what can be done in that situation."