Campaigners are threatening legal action to try to save Grantham's accident and emergency department.
Hospital bosses have confirmed it will be replaced by an Urgent Treatment Centre forcing critically ill patients to go elsewhere.
The United Lincolnshire Hospitals Trust insists the shake up will improve services because the injuries unit will be open 24 hours a day, with only the most serious cases having to be diverted to other hospitals.
But Cllr Charmaine Morgan, from the campaign group SOS Grantham Hospital, said that lawyers are being consulted to see if a legal challenge can be launched.
Two and a half years ago, the unit at Grantham Hospital was closed overnight for an initial three months to improve staffing levels. It was said to be a temporary move.
In August 2016, the Trust announced the A and E unit would no longer open overnight, prompting a series of protests and campaigns.
Grantham Hospital had already lost its maternity unit and overnight paediatric care.
The new plans still need to be approved and there will be a public consultation event held in the town on March 20th.
* Cllr Charmaine Morgan - SOS Grantham Hospital