The union says patients have been left in ambulances for several hours

According to Unison, more than 10 ambulance crews at a time have been known to queue to hand over patients at the East Surrey Hospital, in Redhill.

The trade union said crews often waited up to four hours and were then unable to respond to incoming 999 calls.

Surrey and Sussex Healthcare NHS Trust said it recognised the concerns and was working to resolve the handover issues.

Surrey and Sussex NHS Trust are once again failing in their duty to provide care for their patients Duncan Jones, Unison

Chief executive Gary Walker said accident and emergency staff at the hospital worked incredibly hard to ensure that patients, which numbered more than 300 a day, were seen "quickly, appropriately and with dignity and respect".

"We do not want any patient to wait unnecessarily. The trust and the two local ambulance services are working very closely on resolving the issues of handing patients over to staff."

He added that when delays were anticipated staff worked hard to ensure patients were brought into the hospital as quickly as possible, and that patient safety took priority at all times.

Unison claims the situation has become so severe that many crews end up taking their patients to other hospitals.

Duncan Jones, chair of the Sussex Ambulance branch, said: "Surrey and Sussex NHS Trust are once again failing in their duty to provide care for their patients.

"Trust management have failed to answer our concerns and continue to disguise the problem and not offer the support needed to the hospital staff and ignore the implications of holding up emergency vehicles. This places lives at risk."