Extra intensive care beds would have been available for flu victims if more specialist nurses had been recruited and trained, say nurse leaders.

Pressure on the UK's intensive care units is expected to ease within the next week as flu cases reach their seasonal peak.

However, at one stage only a handful of beds were available, with none free in London.

Christine Hancock, general secretary of the Royal College of Nursing, told the BBC that the problem lay not in a shortage of actual beds, but in hospitals having too few nurses to accompany them.

Intensive care nursing involves having more than one nurse - each fully trained in specialist skills - assigned to each patient at any one time.

Ms Hancock said: "If nurses get sick and patients get sicker there is a real crisis, because there aren't enough to deal with these large numbers of people."

The government has attempted to stem the flow of nurses from the NHS, as well as improve nurse recruitment by encouraging more flexible working arrangements and pay incentives for experienced nurses to return to the NHS.

The number of flu infections has increased, according to the latest figures, but experts say there is little risk of an epidemic.

The weekly statistics released by the Public Health Laboratory Service (PHLS) showed a small increase in the number of people suffering from the virus in England.

In England, the number of reported cases rose from 124 per 100,000 population last week to 144 this week.

Anything less than 400 is not classed as an epidemic.

In Scotland, the number of cases has almost doubled over the last week.

The low number of people going to their GPs earlier in the winter for flu vaccinations has been partly blamed for the problem.

Hospitals are using operating theatre recovery rooms and casualty department resuscitation units to ventilate seriously ill patients.

Many hospitals have already been forced to cancel planned surgery because no intensive care facilities are available for patients following their operations.

Sir Alan Langlands, chief executive of the NHS, told the BBC he was confident people were getting the right care.

He said: "Anyone who will benefit from intensive care is getting that care from the health service."

A spokesman for the London region NHS said: "What we are finding is that there is a particularly nasty viral chest condition going around which is affecting all age groups and causing pneumonia.

"People are coming in very ill and are needing to be ventilated but they respond very well to treatment and after a couple of hours can be transferred back to an ordinary bed."

Some of the pressure had been eased by the NHS Direct telephone advice service which is currently taking 17,000 calls a day - four times the normal level.