New statistics showed that the number of EU nationals working in health and social care has increased by 72 per cent in the last eight years.
An analysis by the GMB union revealed there are now 209,000 EU nationals working in the sector, up from 121,000 in 2009.
EU nationals now make up more than 5 per cent of the entire health and social care workforce, including one in 10 care home staff.
The union said there was already a recruitment and retention crisis in health and social care, raising "serious questions" about the future of the sector while the status of EU nationals remains unclear.
Union urges Government to develop post-Brexit plan for workers in NHS and care sectors
Care workers often do incredibly tough jobs and we rely on people of all nationalities to keep the system functioning
Care workers were identified as a category of worker that the Government needed a strategy for by the Brexit Select Committee in its last pre-election report.
Rehana Azam, GMB’s national secretary for public services, said: "Throughout the election campaign Theresa May hasn't really said anything positive for our five million plus public sector workers.
"The lack of a proper Brexit plan is yet another reason our health and social care sectors are sleepwalking to catastrophe with a Prime Minister who is already letting millions of public sector workers down.
"Care workers often do incredibly tough jobs and we rely on people of all nationalities to keep the system functioning.
EU nationals working in health and social care has increased by 72 per cent in the last eight years Shocking charts show the NHS could be in crisis Thu, February 9, 2017
Get Quotes on Home Insurance
Do these charts prove the NHS is in trouble?
Play slideshow Getty Images 1 of 9
"These latest figures underline the need to secure the future of existing EU workers and to plan properly for the day when freedom of movement ends.
"In recent years our reliance on EU nationals has more than doubled, yet Theresa May seems unable to come up with any kind of coherent plan.
"Whoever forms the next Government needs to clarify the future of EU nationals to ensure our health service doesn't stumble into another catastrophe."
The Recruitment and Employment Confederation has warned that EU citizens are leaving the UK in “droves”, warning that employers are running out of options to fill vacancies, with sectors like the NHS worst affected.