A report by East Midlands Ambulance Service NHS Trust showed that delays at United Lincolnshire Hospitals Trust were double the target set for emergency departments to accept patients.
Bosses at the ambulance trust said that handover and response times remain a “significant challenge” in the region.
But, ULHT officials said the organisation has improved its patient transfer process over the past year.
The handover of patients from an ambulance to emergency hospital department should take no longer than 15 minutes, according to NHS England.
But figures in the report showed that patients waited on average 32 minutes in the final quarter of 2018/19 to be transferred.
Quarterly breakdown (average handover time):
Quarter one – 30 minutes, 53 seconds
Quarter two – 27 minutes, 44 seconds
Quarter three – 28 minutes 49 seconds
Quarter four – 32 minutes, 5 seconds
EMAS officials estimated that delays in handovers lost the trust 15,829 in ambulance response hours last year.
Quarterly hours lost to handover delays:
Quarter one – 4,081
Quarter two – 3,451
Quarter three – 3,735
Quarter four – 4,562
David Williams, Deputy Director of Operations at EMAS, said: “When our crews are delayed at hospital waiting to hand over a patient, they cannot be out in the community helping other people experiencing an emergency.
“We are currently working closely with the hospitals to further improve the patient handover process.”
Chief executive of EMAS, Richard Henderson, raised concerns with ULHT in February this year over delays in transferring patients.
In a letter to ULHT chief executive, Jan Sobieraj, he said the issue could cause “significant patient safety risks to uncovered emergency calls in the community”.
He added that EMAS has often had to care for patients in the back of ambulances.
“While I accept that the position within the emergency department is reflective of a far greater system issue, it remains unacceptable for patients to be held in the back of ambulances,” he said.
But, ULHT said that it had improved its handover times over the past year and that it would continue to work to decrease delays.
A trust spokesperson, said: “Over the last year our ambulance handover times have improved due to the work we’ve been doing with EMAS and NHS Improvement.
“We are doing everything we can to improve handover processes and the flow in and through our departments, and hope to see these times come down even further.
“At times when our emergency departments get extremely busy we can run out of space, which means ambulance crews have to wait until they are able to safely hand patients over to us.
“We always prioritise the most unwell patients, and when a handover cannot take place immediately, staff are allocated to work alongside ambulance crews to ensure those patients waiting are closely observed and any deterioration is dealt with by the most senior clinician in the department.”