Thousands of emergency cases will face longer ambulance journeys from Sunday night.

That is when the Princess Royal Hospital accident and emergency department in Haywards Heath ceases dealing with seriously hurt patients needing emergency surgery.

Critically-ill patients with multiple injuries from around Haywards Heath, Burgess Hill, and surrounding towns and villages like Bolney, Ardingly and Hurstpierpoint and will instead be sent to the Royal Sussex County Hospital in Brighton.

It will add 15 miles and 20 minutes to the journey for many.

Most patients will go straight to Brighton while others may be stabilised at the Princess Royal before being moved.

The number of specialist surgeons at Brighton is being increased to create a specialist trauma centre to cope with the extra demand.

The changes are expected to affect just under 3,000 patients out of the 30,000 which visit A&E at the Princess Royal every year.

The decision to change the rules of admission at Haywards Heath follows the downgrading of accident and emergency services at Crawley Hospital.

This has meant a longer trip to Redhill for some patients.

From Sunday, patients in East Grinstead could find themselves taken to either Redhill or Brighton.

Janine Bell, spokeswoman for the Sussex Ambulance Trust, said: "There are no hard and fast catchment areas.

"The decision over which hospital to take a patient to will be taken by ambulance crews based on clinical needs and particular circumstances. Not all patients will go to Brighton. Some will be closer to Eastbourne, Redhill or Worthing. Brighton will still be closer for many.

"East Grinstead is an example of one area we would expect a crew to use its judgement. We have worked on this together with hospitals and we will be reviewing it as it goes along."

Brighton and Sussex University Hospitals NHS Trust, which runs both hospitals, insists the changes are not a downgrade for the Princess Royal and each hospital will carry on providing a 24-hour A&E service.

It says taking patients on a longer journey to a place where a specialist team is on hand will mean they have a better chance of the best care.

However some in Mid Sussex believe the change is the start of a long process which will end with the loss of A&E at Haywards Heath.

They refer to the fatal A23 crash at Pyecombe in May 2004 in which eight people died. Two crash victims were taken to the Princess Royal but if the same thing happened again they would all go to Brighton.

Christine Hanson, 45, from Burgess Hill, said: "They can dress it up how they like but as far as I am concerned it is taking something away from the Princess Royal and therefore a cut in service.

"It won't be long before we are hearing about delays and problems these changes will bring."

Ambulance crews are also uncertain about the plans and there have been fears that taking people on longer journeys might put them at risk.

Sussex Ambulance Unison said paramedics were better equipped to deal with both minor and major injuries but greater investment was needed.

Paramedic David Davis, a Unison member, said: "This is going to put more pressure on us. When you increase the mileage you are always going to decrease the number of patients we can deal with."

A&E at Haywards Heath will continue to treat patients for a number of emergencies including burns, eye injuries, broken bones, chest pain and heart attack, stroke, minor head injuries, asthma attacks and overdoses.