David Cameron was met with verbal disdain as he attempted to defend his government's record on the NHS in front of a group of pensioners.
Angry attendees at the Age UK conference heckled, jeered and booed the prime minister as he faced awkward questions over nurses' pay and prescription charges.
The Tory leader was asked how he would stop NHS nurses from quitting the organisation and take on similar roles as agency staff.
Cameron argued well-run hospitals would be less reliant on agency workers and suggested management practices could counter the problem.
"The truth is well-run hospitals will be less reliant on agency staff, and so what we need to do is make sure there are good managers planning for the capacity they need, rather than rushing around hiring agency staff," he said.
"I'll never forget sitting in a hospital talking to an agency nurse who said she was sick that so many agency nurses are used as it is 'such a waste of money for the NHS'. We need to make sure all hospitals copy the best hospitals that are less reliant on the NHS."
But some audience members accused Cameron of not adequately answering the question and urged the prime minister to do so.
Cameron then argued you "can't blame" doctors and nurses choosing to working in another hospital. He stressed NHS managers needed to plan their care "more carefully" to sure-up their workforce.
Labour seized on the reception the prime minister received at the event and claimed Cameron cannot "shake off his betrayal of the NHS".
"Under him, people are waiting a week or more for GP appointments, A&Es are in crisis and hundreds of thousands of vulnerable older people have lost social care support," Jamie Reed MP, Labour's shadow health minister, said.
"The NHS can't afford the Tories' plan for deeper care cuts in the next Parliament. Cameron has broken his promises on the NHS and has proven he can't be trusted with it."
The incident comes with less than 50 days to go before the general election in May, with Labour and the Tories level-pegging (34% vs 34%) in the latest opinion poll from YouGov. The study, which surveyed more than 1,600 voters between 22 and 23 March, also put Ukip on 12%, the Liberal Democrats on 8% and the Greens on 6%.