Thousands of nurses were denied permission to work in England last year, despite hospitals facing staff shortages, new figures show.
The Royal College of Nursing (RCN) has found that the refusals have hit high profile hospitals in Cambridge, Newcastle and Manchester.
A Freedom of Information request to the Migration Advisory Committee (MAC) found more than 2,341 refusals.
The government said the MAC was reviewing its refusal policy.
The RCN asked for the number of applications to allow overseas (non-European Union) nurses to work in England between April and November 2015 and the number refused.
It found that East Lancashire Hospitals NHS had the highest number of refusals with 300 out of 300 applications.
The research found that Brighton and Sussex University Hospitals and North Cumbria University Hospitals both had about 240 refusals.
Snapshot of FOI request results
Nursing was temporarily placed on the MAC shortage occupation list (allowing more overseas nurses) in December.
Janet Davies, chief executive of the RCN, said: "These figures show that when nursing is not on the list, many trusts are unable to recruit enough nurses, which could have an impact on patient care."
Catherine Morgan, director of nursing at The Queen Elizabeth Hospital in King's Lynn, told the BBC she had been prevented from recruiting a number of overseas nurses.
"It is frustrating because we are running a hospital and do want it to be safe, and we had the opportunity to recruit from India and the Philippines and we had nurses keen to come over but haven't been able to bring them over," she said.
A Department of Health spokesman said: "The MAC is currently reviewing the shortage occupation list. Staffing is a priority and there are already more than 8,500 more nurses on our wards since 2010 and 50,000 more nurses in training.
"We want more home-grown staff in the NHS and our recent changes to student funding will create up to 10,000 more nursing, midwifery and allied health professional training places by 2020."