Brexit could have a "huge impact" on the NHS workforce, a leading auditor has warned as figures show that one in every 20 NHS workers in England come from the European Union.
Fresh analysis of workforce statistics show than 57,608 workers in the health service in England come from the EU - or 5% of the total workforce,
Analysis by the Press Association found that 9% of NHS doctors come from the European Union, with particularly large numbers of Greek and Irish nationals.
Data from the Health and Care Information Centre show that in March, 21,032 nurses and health visitors come from countries within the EU - or 7% of the total number of workforce.
Almost 12,000 EU nationals work in support roles for clinical staff and more than 6,000 work in "NHS infrastructure" jobs including 456 NHS managers.
Commenting on the outcome of the referendum, Jason Parker, head of healthcare at auditor KPMG, said: "Today's economic uncertainty as a result of Brexit has a potentially huge impact on the NHS's workforce. The health sector is enormously reliant on workers from the European Economic Area. We will be advising our clients to look after and reassure these highly skilled and valued workers.
"We expect there to be further implications for research and innovation in the NHS, as many collaborations and employees in this domain rely on existing links with the European Union.
"NHS leaders will be hoping that the Brexit camp stay true to their word to redirect some of the capital linked to the European Union back into the NHS, however whether that is financially practical remains to be seen."
NHS England's medical director has called on NHS leaders to make European staff "feel welcome" in the wake of the result.
Professor Sir Bruce Keogh told the Health Service Journal (HSJ): "It is really important we make them feel welcome. If you are a European doctor or nurse you might not feel too welcome at the moment.
"The essence of delivering high quality care is dependent on a workforce that feels valued and secure."
Danny Mortimer, chief executive of NHS Employers, told the HSJ: "The NHS has always needed to supplement UK trained staff with people from across the globe.
"Leaders across the NHS need to let the EU nationals in their teams know how valued this contribution will continue to be."
Meanwhile, leading midwives have expressed fears over the impact Brexit will have on NHS finances.
In a statement, the Royal College of Midwives (RCM) said: "The vote is likely to result in a period of considerable uncertainty for the UK. Whilst it will be some time before the full economic, political and social implications become clear, the impact that this will have on public finances and the funding of the NHS remains of concern to the RCM."
And the British Medical Association (BMA) has urged politicians "not to play games" with the health service in the aftermath of the referendum.
As a result of the country's decision to leave the EU, health regulators may have to change the way information about medics is shared across European borders when concerns are raised about doctors or nurses.
At present, there are European directives on sharing disciplinary records and fitness to practise hearings.
Niall Dickson, chief executive of the General Medical Council, said: "Withdrawing from Europe will have implications for the way that we regulate doctors but we understand that the vote to leave the EU will have no impact on the registration status of any doctor already on the register.
"We will now explore how doctors from the EU will be granted access to the UK medical register and how any concerns about those doctors will be shared between us and other countries. We will also seek to understand the implications for UK doctors wishing to work in the EU once the UK is no longer a member state."
Jackie Smith, chief executive of the Nursing and Midwifery Council (NMC), said: "We will be working closely with the Government and other partners to understand the implications of the UK's negotiated withdrawal from the European Union on our work. However, there will be no immediate impact on the NMC in terms of our role as the UK-wide regulator for nursing and midwifery."
Meanwhile, Nigel Farage has said that the official Leave campaign's call to spend £350 million a week extra on the NHS with money saved from contributions to the European Union was a "mistake" and cannot be guaranteed to happen.
The Ukip leader was not part of the Vote Leave campaign which emblazoned slogans such as "We send the EU £350 million a week, let's fund our NHS instead" and "Let's give our NHS the £350 million the EU takes every week" on buses and posters.
The figure has twice been described as misleading by the UK Statistics Authority watchdog because it referred only to the UK's £19 billion gross annual contribution and did not take into account Britain's rebate or money that comes back from the EU. When these factors are included, the net cost was around £7.1 billion a year - or £137 million a week.
Asked on ITV's Good Morning Britain to guarantee the money would go to the NHS, Mr Farage said: "No, I can't and I would never have made that claim - it was one of the mistakes that the Leave campaign made."