The former A&E department at Pontefract Hospital has been re-classified as an urgent treatment centre.
The centre, which treats people with non-life threatening conditions, launched on Monday and will be open 24 hours a day, every day.
Pontefract will treat people for illnesses and minor injuries and will continue to do blood and urine tests and X-rays, whilst A&E at Pinderfields is targeted at critical or life-threatening conditions.
Mid Yorkshire Hospitals Trust insisted no changes were being made to the service at Pontefract and the name change was to guide patients to the right place for treatment.
The Trust said: “The UTC is for people who have less serious conditions and are unlikely to need to be admitted to hospital.
“It offers fast access to the same wide range of specialist tests and treatment that have been available at Pontefract for many years. Keeping Pontefract as a 24/7 service for people with urgent health needs means we can make the best use of the facilities and workforce we have in the district.”
The Pontefract and Castleford MP, Yvette Cooper, is among people who have raised concerns that patients will face longer waiting times at Pinderfields A&E.
She said: “Bit by bit they are just pushing more and more patients into going all the way to Pinderfields when they could and should be treated here.”
Trudie Davies, Mid Yorkshire’s chief operating officer, said: “This should not result in more people going to Pinderfields, but what it should do is help people make a better choice about where they need to access the care that they are seeking.”