Health service leaders have urged politicians to address a staffing crisis which is harming patient care in hospitals.
A report by NHS Providers, the body which represents health trusts, said low pay and stressful working conditions were leading to hospital staff leaving their jobs.
The warning was made as latest figures showed continuing staff shortages at Mid Yorkshire Hospitals trust, which runs Pontefract, Pinderfields and Dewsbury hospitals.
A report to the trust board said there had been an increase in wards reporting staffing at 80 per cent of the required level.
There were almost 230 nursing and midwifery vacancies at the trust in March.
Around 60 student nurses had applied for jobs at the trust.
But staffing the report said: “Past experience indicates that a proportion of these staff may not commence employment with the trust, as they will be applying for multiple posts.”
In a staff survey for the last quarter of 2016-17, just 22 per cent of Mid Yorkshire employees who took part said there were enough staff for them do their job properly.
Concerns have also been raised that nurses recruited from Spain to plug staffing shortages could leave because of uncertainty over Britain’s vote to leave the European Union.
Chris Hopson, chief executive of NHS Providers, said a pay freeze was making it difficult for NHS organisations to retain staff.
Mr Hopson said: “Significant numbers of trusts say lower paid staff are leaving to stack shelves in supermarkets rather than carry on working in the NHS.
“And we are getting consistent reports of retention problems because of working pressures in the health service causing stress and burnout.”