An analysis of NHS figures by anti-Brexit campaigners predicts there will be 17,644 nurses and midwives from the EU working in the health service in December 2022 compared with 23,582 in September 2016.
Royal College of Midwives chief executive Gill Walton said: “These figures should be a wake-up call to anyone who loves our NHS."
“It’s now clear that the staffing crisis in our health service is made worse by Brexit, not better as we were told.”
Research found 1,400 fewer midwives and nurses from EU working in the NHS since the 2016 referendum.
Forecasts in the NHS Digital Workforce Statistics, analysed by the People's Vote Campaign, show the NHS stands to lose another 4,512 EU midwives and nurses by 2022, bringing the total lost since Brexit to 5,937.
Vacancies are predicted to soar 14,788.
The warnings come after the Nursing and Midwifery Council revealed in March that almost 4,000 European Economic Area health staff left their register in the previous year, with 47% citing Brexit as one of their main reasons for leaving the UK.
Ms Walton added: “Our NHS needs more midwives and other healthcare professionals from EU countries, not fewer – but since the referendum we are now sadly seeing people leaving.
“Not a day goes by without new facts emerging that show the Brexit people were promised can simply not be delivered.”