The flu crisis could become the most severe for 10 years, according to Health Secretary Alan Milburn.

Figures announced by Mr Milburn showed cases of flu continuing to rise steeply, and he revealed that in some areas, patients had been sent to private hospitals for treatment.

NHS hospitals in England, Scotland, Wales and Northern Ireland have already been stretched to the limit by large numbers of seriously-ill patients, and the situation is not expected to ease quickly.

Mr Milburn said that although the outbreak was not expected to match Britain's last epidemic, in 1989 and 1990, it could still be the most serious since then.

He told the House of Commons: "We could be heading for the worst outbreak in the last decade. The evidence suggests that the NHS is dealing with these pressures well."

But Shadow Health Minister Dr Liam Fox hit back, accusing the government of "complacency", in failing to prepare the NHS for extra flu cases.

He said: "NHS staff are coping tremendously well but they are being badly let down by the people who run the service."

Earlier government claims that flu had reached epidemic level were strongly criticised.

The government's Chief Medical Officer Professor Donaldson said at the weekend that the health service had been confronted with a "serious epidemic".

The Conservative Party said this is a "convenient excuse" for the failure of the NHS to cope with a normal seasonal surge in flu levels, due to underlying problems such as shortages of beds and nurses.

However, Health Minister John Denham told the BBC that Professor Donaldson was an "independent adviser" to the government.

He added: "What we're seeing is not a normal winter but a very serious increase in the number of people with flu."

Interim figures from the Royal College of General Practitioners (RCGP), who are in charge of counting flu cases, suggest that the UK still falls well short of what is officially regarded as an epidemic.

Tory health spokesman Dr Philip Hammond said: "This was rather convenient for Alan Milburn to find he could describe this as an epidemic, just at a moment when he was very much on the back foot to explain why the NHS has been plunged into such crisis from an entirely predictable outbreak of disease."

Professor Donaldson said that the official figures were too low because they did not take into account those people who rang NHS Direct helplines in their area for advice.

But Dr Ian Bogle, Chairman of the British Medical Association said: "I do not think the epidemic exists. A lot of people phoning NHS direct say they have flu but I suspect they don't."

Under pressure

There is no doubt, however, about the pressure flu has placed on the health service.

GPs have been inundated by victims while an influx of seriously-ill patients cut the number of available emergency hospitals beds in the UK to as few as 21 over the weekend.

The latest outbreak has already claimed scores of lives, including some younger, fitter, patients.

Former Welsh international rugby player Kieron Gregory, 33, died at home following a hospital check-up for flu.

The hospital has insisted that he was not sent home because of a shortage of beds or staff.

Figures rising

The last official figures released by the flu monitoring service put the number of cases per 100,000 people at 144, although the interim results for the most recent week are thought to have increased this to approximately 200.

The official threshold for an epidemic in England, Wales and Northern Ireland is 400 cases per 100,000.

The last declared epidemic, in 1989/90, saw a peak of 534 cases per 100,000, and saw 29,000 flu-related deaths were reported.