A judge could be asked to look into the legality of the temporary closure of a North Yorkshire A&E department to critically-ill patients.
NHS campaigners have applied to the High Court for a judicial review of the suspension of A&E services at Northallerton's Friarage Hospital.
South Tees NHS Foundation Trust decided to close the A&E to the most seriously-ill patients after problems recruiting enough medics at the hospital.
Safety fears have been raised over the move, which means some patients are being diverted to Middlesborough or Darlington, both around 30 minutes away by car.
Action group Save Friarage Hospital hopes to overturn the move after launching legal proceedings, backed by law firm Irwin Mitchell. Today's judicial review application, if granted, could see the legality of the temporary closure tested in court.
Irwin Mitchell lawyer Helen Smith said: "This issue goes beyond the pure health services on offer in Northallerton, as the suspension would undoubtedly affect ambulance services, other local hospitals and the rural communities in a number of different ways.
"There has been no formal public consultation. With this in mind, our client’s believe there is a need to re-instate the hospital services and revisit the original decision.
“We appreciate that the NHS faces difficult challenges, but it is clear that any decision on the future of services must always put the best interests of patients first and follow a fair process.”
Campaigners are concerned that the temporary closure, which NHS bosses said would be reviewed in six months' time, will become permanent.
It is also feared that patients in remote parts of the Yorkshire Dales will have too far to travel if they need emergency treatment.
Holly Wilkinson of the Save Friarage Hospital Group said: “We believe this suspension of A&E services could put lives at risk and we have been left with no choice but to instruct Irwin Mitchell. We want to have our voices heard on this issue and now believe that legal action is the only way forward on the matter.
The A&E at Friarage was temporarily changed to an urgent treatment centre from March 27.
South Tees NHS Foundation Trust said around eight patients a day would be diverted to other hospitals, mainly James Cook Hospital in Middlesborough.
Trust bosses pointed out that most patients with life-threatening conditions were already taken straight to Middlesborough or Darlington Memorial Hospital.