The biggest ever rise in public dissatisfaction with the NHS was recorded last year, according to a long-running survey.
The British Social Attitudes Survey has been tracking satisfaction since 1983.
The 2015 poll of nearly 2,200 people showed satisfaction with the NHS at 60% - down from a peak of 70% in 2010.
Some 23% said they were actively dissatisfied - a rise of eight percentage points on the year before and the biggest single jump in a year.
Waiting times were cited as the biggest reason for dissatisfaction - mentioned by over half of people - followed by there being not enough staff.
The findings come amid growing pressure on waiting times for cancer care, A&E and routine operations, such as knee and hip operations.
Patients reported highest satisfaction rates for GP services and lowest for social care, which is run by local authorities and covers home help for tasks such as washing and dressing, and care homes.
The survey - carried out by NatCen Social Research - covered Scotland, Wales and England. The differences between the three nations were not considered to be statistically significant.
Chris Ham, chief executive of the King's Fund think-tank, said that while overall satisfaction levels were still high by historical standards, the findings should act as a "real wake up call".
"What's gone wrong is the public's perception of the NHS under growing pressure. Money is tight, waiting times are getting longer, people are concerned that when they need the NHS it might not be there for them."
Rob Webster, chief executive of the NHS Confederation, agreed the public needed reassurance about the future of the NHS.
But he said the "most important set of results" were on social care. He said the satisfaction levels were "deeply concerning" and said the system needed greater funding.
A spokesman for the Department of Health in England said: "There is pressure on the NHS as our population ages, and that's why the government is investing record amounts to transform care."
A Welsh government spokesman said it too was increasing the budget, and ministers were working hard to "improve patient care", while the Scottish Health Secretary Shona Robison said ministers were always "open to patient feedback".