Hundreds of patients were left waiting up to an hour in ambulances outside Doncaster and Bassetlaw Teaching Hospitals this winter, contravening a key NHS safety standard.
Unison said delays risk patient safety and are “a waste” of ambulance crews’ skills.
Ambulances took 8,271 patients to emergency departments at the Doncaster and Bassetlaw Teaching Hospitals NHS Trust between December 3 and February 3, according to NHS Digital data.
Of those, 562 waited between 30 and 60 minutes before A&E staff were able to take over from paramedics, while 56 arrivals waited for more than an hour.
Despite the NHS saying a delay of just 15 minutes is a potential threat to life, 27 patients waited up to an hour in a single day when the problem was at its most severe.
The overall number of delays at Doncaster and Bassetlaw Teaching Hospitals has dropped since 2017-18.
Over the same period last winter, 822 patients waited in ambulances for 30 minutes or more, 25 per cent more than this year.
Across England, nearly 100,000 people waited for 30 minutes or more between December and February – one in 10 arrivals.
David Purdue, chief operating officer at DBTH, said: “In December and January, 103 out of 7,911 patients waited between 30 and 60 minutes before a care hand-over was completed with our emergency department team.
“While we would prefer that all patients are transferred immediately, due to demand sometimes this isn’t possible.
“When this occurs, individuals are moved to the ambulance bay.
“This is a special area within our hospital where paramedics can monitor their condition until our staff are ready for the hand-over process.
“Our ambulance transfer times are one of the best in the region and we work in close partnership with our transport providers, with staff available should waiting patients need them.”
David Williams, deputy director of operations at East Midlands Ambulance Service, said: “When our ambulances are waiting to hand patients over at hospitals they are unable to respond to new 999 calls.
“Subsequently, patients in the community may experience a delayed response to their 999 call until we have an available resource.
“We continue to work with our NHS and social care partners, including the hospital emergency departments to improve the welfare of our patients and the patient’s experience.
“We also continue to escalate our concerns to our commissioners and regulators about patient safety.“