There are not enough nurses to properly care for patients at a Carlisle hospital's accident and emergency department, a report suggests.
The confidential document, seen by the BBC, highlights a "significant deficit" in nursing numbers and skills at the Cumberland Infirmary.
The North Cumbria Hospitals NHS Trust has been forced to draft in extra hospital staff from Whitehaven to cope.
It said it was trying to recover from shortages over the winter months.
The report, produced by the trust's chief matron Lynn Anderson, said: "Bank, extra hours, overtime and agency have all been utilised, however none of these solutions have provided a sustainable solution."
It said cover had been provided in the last few weeks by volunteers from Whitehaven's West Cumberland Hospital.
'Will occur again'
It went on: "There are no further volunteers at this point, and therefore this leaves a significant deficit in nursing numbers and skills mix to provide adequate care to those patients requiring emergency intervention and rapid response to presenting emergencies.
"Delay in intervention leads to patients, at times, not receiving care in a timely manner."
Trust chief executive Stephen Eames said: "During the winter months there have been occasions when we have experienced a shortage in nursing staff in one of our A&E departments when the other department was fully staffed.
"As this is likely to occur again in the future, and we have some historical arrangements in place which are site specific, we are working to address this to ensure this is consistent for all staff."
The Royal College of Nursing (RCN) said "Like the NHS across the country, the North Cumbria University Hospitals NHS Trust continues to suffer with significant nursing shortages."