Nursing leaders have warned that the NHS "would not cope" without staff from abroad, as new figures suggest the number of EU nationals joining NHS hospitals has soared.
Around one in five nurses recruited in England 2015/16 were non-British EU nationals - up from one in 14 in 2011/12.
Over the same period the proportion of British nurses joining hospitals dropped from roughly 78% to 70%.
The Royal College of Nursing said the figures showed nurses trained abroad made a "critical contribution" to the health service, while the British Medical Association said the NHS could only benefit from widening its overseas "talent pool".
New analysis by the Press Association has revealed the extent to which the NHS in England is increasingly dependent on EU workers to meet demand for new staff.
Of the 33,000 nurses recorded as joining hospitals in 2015/16, just over 6,000 held an EU nationality other than British. Some 1,750 were Spanish, 1,300 Italian and nearly 1,000 Portuguese.
The findings, based on data published by NHS Digital, also suggested that in 2015/16:
:: Around one in 10 midwives joining hospitals were non-British EU nationals, up from one in 20 in 2012/13
:: Some 20% of newly-recruited speciality doctors were EU nationals, along with 17% of speciality registrars and 7% of foundation year doctors
:: Just over 10% of the total staff joining NHS hospitals held EU nationality. In 2012/13 the proportion was 6%.
The rights of EU citizens to continue to work in the UK is likely to be one of the key areas of the Brexit negotiations. The Government has yet to clarify the future status of the 2.2 million non-UK nationals employed in this country.
Health Secretary Jeremy Hunt this week told the Conservative party conference that he wanted EU nationals working in the NHS "to be able to stay post-Brexit".
Responding to the PA's analysis, Donna Kinnair, director of nursing, policy and practice at the Royal College of Nursing, said: "Nurses trained in other countries have contributed to the NHS since its inception.
"The health service would not cope without their contribution, and with the future supply of nurses looking uncertain this situation will not change any time soon.
"Allowing the ambiguity about the future of health care staff from the EU to continue is completely unfair.
"The Government must act now and develop a coherent and sustainable workforce strategy, which recognises the critical contribution of overseas nurses as well as the pressing need to educate, recruit and retain a domestic nursing workforce in the UK."
Dr Mark Porter, British Medical Association council chair, said: "The UK has grown to rely on health care workers from the EU who play a vital role in the effective functioning of our NHS.
"By widening our talent pool, the NHS can only benefit from the wealth of knowledge and expertise that is gained from recruiting doctors from overseas.
"With unprecedented staff shortages and a recent BMA study revealing that almost half of doctors were planning to move abroad to work, the Government should be focusing on creating a health service that supports and nurtures both those wishing to apply to work in the UK and those already here."
The proportion of EU nationals recruited as nurses in 2015/16 may be even higher than one in five, as the data from NHS Digital includes 1,674 nurses whose nationality was recorded as "unknown".
NHS Digital also noted that data on nationality was based on self-reported information from individual employees. As this may reflect cultural heritage rather than country of birth, the figures do not necessarily equate to migrants from other countries.
A Department of Health spokesman said: "As the Secretary of State has repeatedly made clear, overseas workers form a crucial part of our NHS and we value their contribution immensely.
"We want to see the outstanding work of nurses who are already trained overseas continue, but at the same time we are already delivering our plan to train more home-grown nurses - there are over 10,700 additional nurses on our wards since May 2010 and 50,000 in training, and our changes to student nursing, midwifery and allied health professionals funding will also create thousands more training places by the end of this parliament."