The Accident and Emergency department at Weston General Hospital will begin overnight closures from tonight.
It will shut between 10pm and 8am, meaning patients will have to travel to Bristol or Taunton for emergency treatment.
The health trust says it's a temporary move after a damning Care Quality Commission report was published.
During the inspection health watchdog officials found the A&E department in such disarray that they issued a warning notice requiring immediate improvement.
Overall the Trust requires improvement but the urgent and emergency service is rated as inadequate, with CQC inspectors revealing they are "very seriously concerned" about the service.
Mary Cridge Head of Hospital Inspections for the CQC in the South West told ITV West Country that specialists on the inspection visit were surprised to find a corridor in the A&E Department was in almost permanent use to treat patients when the department was busy.
This caused real concerns regarding the safety, privacy and dignity of the patients receiving care there.
The Care Quality Commission has advised that recruiting doctors to the emergency department and employing the right mix and grade of permanent staff has to be the long-term solution.
Last month the hospital's Chief Executive James Rimmer admitted that urgent care at the hospital has been "fragile" for several years.
Demonstrators have gathered outside the hospital to protest against the closures.