Calls to NHS Direct have rocketed by 50% in the past few days, leaving the helpline at "breaking point", it has been claimed.
The call service is under huge pressure as flu infection rates more than doubled in the last week, the Daily Mail reports.
Patients were having to wait two days to speak a nurse with as many as 46,000 people calling the helpline last weekend at a rate of almost 960 an hour, it said.
A senior nurse told the Mail: "This is by far the worst it has ever been. People have not been receiving call-backs for 48 hours - it's appalling."
On Tuesday the Department of Health announced that 302 people were currently in intensive care with flu while 17 people had died. Swine flu is still the most dominant strain of flu this winter, but there are other types, including type B.
But a Department of Health spokeswoman said the health service was coping "very well" with the outbreak of flu.
She said: "We are currently seeing an unusually high number of people in critical care with flu. But the NHS is well-prepared.
"There is always more pressure on the NHS at this time of year and this year is no different. But the NHS is coping very well with only a small percentage of the intensive care capacity being taken up by patients with flu.
"However, as a cautionary approach, local health trusts are looking at how they can increase capacity if necessary.
"Prevention is better than cure - it's very important that people who are at risk have their free seasonal flu vaccination. All pregnant women should have the flu jab - at any stage of pregnancy. If you are eligible contact your GP or practice nurse now to get your seasonal flu jab."