Shadow Health Secretary Andy Burnham has accused David Cameron of "putting the NHS in intensive care", following the release of new A&E figures.
Tens of thousands more patients waited for longer than four hours to be seen at Accident & Emergency departments between October and December last year, according to figures revealed by NHS England.
The data showed 407,844 people were left waiting for longer than the target time to be seen by a doctor, compared with the same quarter in 2013.
There was also a steep rise in the number of patients who had to wait for 12 hours on a trolley until a bed was free, up to 20,962 from 5,573 in the same weeks last year.
The numbers on waiting times provoked a strong reaction. Attacking the government for cuts to social care and a reorganisation of services, Burnham said: "The prime minister's central promise at the last election was to protect the NHS.
"It is now clear for all to see that he has put it in intensive care. Patients and the public, whose hospitals are in danger of being overwhelmed, need answers today and what he will do to turn things around."
Health Secretary Jeremy Hunt claimed on Radio 4 this morning (Tuesday 6 January) that the figures showed waiting times were among the best in the world. But this claim appears to have been unsubstantiated by official research.
Burnham said: "We have repeatedly warned David Cameron to get a grip on the growing crisis in A&E and ambulances services. He has failed to do so and has now left patients all over England exposed to unacceptable levels of risk.
"It beggars belief that, only yesterday, on the day when hospitals were declaring major incidents, Jeremy Hunt was asking officials to email hospitals asking for ideas in four bullet points on how to solve the winter crisis.
"There could be no clearer illustration of the government's failure to plan and get ahead of the very serious situation in which the NHS now finds itself. It smacks of panic when what is needed is planning and leadership."