Three in four people do not think there are enough nurses to care safely for patients in the NHS, a survey suggests.
The poll of 1,600 UK adults – carried out by YouGov for the Royal College of Nursing – found 74% were concerned about staffing levels.
Latest figures for England show one in nine posts is vacant.
The RCN branded the situation dangerous, but ministers said steps were being taken to recruit more nurses.
Chief among their plans is the pay offer on which nurses are currently being balloted. Ministers have offered nurses a minimum of 6.5% over three years.
The RCN is asking its members to back that offer, but described the current staffing situation as "inevitable" given the "short-sighted" cost-cutting of recent years.
Pay has been capped or frozen since 2010 and training opportunities restricted, which, the union says, is to blame for the growing numbers of nurses leaving the profession.
In a speech to launch the RCN's annual conference, being held in Belfast this year, its general secretary Janet Davies will say: "This is a failure of politicians and policymakers – with an inability to recognise the value of nursing, an unwillingness to listen to those of you who are working in the service and a lack of political will to address it.
"The current shortages are not only dangerous, but a vicious circle too.
"Poor staffing levels are the number-one reason for working-age nurses leaving the register.
"Good nurses do not want to do a bad job."
'I feel like a failure'
The RCN wants to see safe staffing legislation introduced across the UK after Wales became the first country in Europe to introduce such laws in 2016.
Scotland has already promised it will follow suit, but Northern Ireland and England have not committed to it.
As part of a report on staffing to open the conference, the RCN released feedback from their members outlining the problems they were facing.
This included evidence of patient care being compromised, being overburdened with paperwork and not having time to take breaks or eat.
They said the pressures meant healthcare assistants were being asked to fill in for nurses at times.
One said: "Vital medication was missed during this shift as I had too much on my mind.
"I missed breaks and I went home feeling hungry, tired and like a failure. I am looking for a new job leaving nursing."
A Department of Health and Social Care spokeswoman said steps were being taken to recruit more nurses, acknowledging "the NHS would collapse without our wonderful nurses".
As well as the pay rise, the spokeswoman cited the 25% increase in student training places which is happening this year and greater flexible working opportunities that are being introduced.