The Accident and Emergency (A&E) department at Chorley Hospital in Lancashire will close temporarily from Monday because there are not enough doctors to cover the service.
Lancashire Teaching Hospitals NHS Trust said they did not have enough emergency medicine staff after April 18 and "there are no other safe options for delivering care".
The A&E will be temporarily replaced with an "urgent care service" and the "vast majority" of patients who normally attend the department will be treated appropriately under the new arrangement, the trust said.
The new service will be open between 8am and 8pm.
From Monday, 999 ambulances will take patients to the Royal Preston Hospital or other nearest appropriate hospitals rather than Chorley.
The trust said it had become increasingly difficult to staff the middle grade doctor rota at its emergency departments and it currently has only eight of the 14 doctors needed.
Local MP Lindsay Hoyle blamed the trust's management for the crisis and said he had even suggested calling in military medics to see the department through its staffing problems.
The plans to close A&E at Chorley are a reflection of poor planning, a failure to recruit and a continual trend of services being shifted from Chorley to Preston.
The Royal College of Emergency Medicine said the situation at Chorley "is a reflection of the national picture of A&E services".
If a department is already running on minimal staffing levels and further rota gaps appear it becomes impossible to maintain the service. The situation has been exacerbated by the capping of agency recruitment and in the short term has proved to worsen the problems it seeks to solve.