A new report calls for a dramatic reduction in the number of accident and emergency units.
NHS medical director Professor Sir Bruce Keogh said change was needed to ease pressure on an emergency service at its limit.
Halifax MP Linda Riordan has raised concerns that the Calderdale Royal Hospital A&E unit could be one of those at risk.
Sir Bruce said the current system was under intense, growing and unsustainable pressure caused by increasing numbers of people turning to A&E, an ageing population and confusion over existing services.
His report calls for an overhaul to treat more people in their own homes and keep them out of A&E.
For those who do need to go to hospital for emergency treatment, he said two types of A&E should be created – emergency centres for assessing patients and starting treatment, and major emergency centres providing specialist care, such as for strokes or heart attacks.
He said between 40 and 70 major A&Es would be needed – potentially reducing the number providing a full service in Yorkshire by about half.
Sir Bruce insisted the changes were not about closing local A&E units but about creating a safe service that could cope with increasing demand.
The review has been triggered by a growing crisis engulfing emergency care services amid predictions of a difficult winter ahead for the NHS.
Sir Bruce said: “We are here really because A&E is creaking at the seams. It’s not broken but it is struggling.
“When A&Es become very busy it means other parts of the system are creaking as well, they are under stress. It’s against that background that there’s a feeling this winter will be difficult.”
Shadow Health Secretary Andy Burnham welcomed the findings but warned Ministers needed to act now.
“They are forcing A&Es to go into winter with too few nurses, doctors and beds,” he said.
Health Secretary Jeremy Hunt said the review would mean taking difficult decisions.
“We all know that the NHS needs to change to meet the needs of an ageing population,” he said.