The Westmorland General Hospital's mental health ward could close.
The Cumbria Partnership NHS Trust - which runs the Kentmere Ward - doesn't have the money to upgrade it to meet Care Quality Commission guidelines.
Local MP Tim Farron's launched a campaign to save the unit, which is also know as ward 4.
He's begun an online petition and written to local health bosses and government ministers to stress its importance.
Mr. Farron said: “Mental health services are absolutely critical. Local people in vulnerable situations rely on these services, and government cuts cannot be allowed to push this ward into closing. The long-term effects of closing the unit would be far greater than the short-term savings, as access to mental health services would deteriorate. If the ward is closed, vulnerable patients will have to travel long distances to access the services they need.
“A recent CQC report raised a number of important points about the Kentmere Ward, and these improvements must be made, but there can be no question of the ward closing either temporarily or permanently. What is needed in our area is not for this ward to close, but for it to improve.
“For many years, the Lib Dems have worked to push mental health up the agenda. Closing this ward would be a backwards step for mental health care in South Lakeland. I will fight these plans, to ensure that local people can access the mental health services they need.
“Ten years ago we successfully fought to save Ward 4 – I am determined that together we can do so again.”