Staff at Royal Preston Hospital have been reduced to tears by 'frustration and anger', as A&E patients regularly wait more than two days to be admitted to wards.
Some senior members of staff have raised concerns in a letter to bosses at Lancashire Teaching Hospitals Foundation Trust.
The managers have raised concerns over a lack of support from the rest of the trust and say that ambulances are regularly facing waits of more than four hours to hand over patients.
Meanwhile, they also say it has become commonplace for more than 50 patients to be waiting for beds at the same time and that they wait for more than 60 hours to make it to a ward.
The letter - dated 30 March - is signed by clinical director Graham Ellis, two unit managers, the specialty business manager, and the matron.
Details of the letter were first published by the Health Service Journal (HSJ), which pointed out that clinicians have been raising safety concerns about the emergency department for several years behind closed doors, but have not before gone public.
In response, the Trust's CEO Kevin McGee said patient safety and staff welfare were top priorities and noted that all NHS hospitals were facing similar pressures.
In the letter, the managers say the emergency department’s situation is "increasingly precarious".
They wrote: "For the past few months we have on a regular basis had more than 50 patients waiting for a bed and that wait being in excess of 60 hours.
"This means that at most times there is limited or no space to accommodate newly acutely ill patients causing ambulance handover delays of over four hours and delay in treatment."
The letter continues: "This has a huge impact on members of staff who are working extremely hard but complete their shifts knowing they haven’t provided the care they would want to, are physically and mentally drained and despite their best efforts have seen patients suffer and have received negative comments from distraught relatives and carers. We have witnessed senior experienced staff crying with frustration and anger..."
According to the HSJ, the trust acknowledges there is an "urgent need" to improve the emergency department infrastructure, as it is too cramped for the volumes of patients it receives.
In a statement to the journal, the trust's CEO Mr McGee said: "The safety of patients and the welfare of staff remain the trust's top priorities and we would like to express our ongoing thanks to our emergency department colleagues who continue to demonstrate commendable resilience and compassion to each other and our patients in very challenging circumstances.
"Like NHS providers across the country, our hospitals have continued to sustain unprecedented pressure which has been exacerbated by the pandemic.
"Lancashire Teaching Hospitals has established and robust processes in place to ensure patient safety and discussions have taken place between emergency department clinicians and trust leadership to help collectively agree approaches to reduce the impact of concerns raised."
Lancashire Teaching Hospitals Foundation Trust has been approached for further comment.