The death toll from the swine flu virus has doubled in just three days to 14, the government said yesterday.

The figure has risen dramatically since Tuesday when seven people were known to have died from the H1N1 virus. A week ago, the total was four.

The UK now has the third highest number of cases worldwide, after the US and Mexico.

Although 335 people are hospitalised in England, with 43 of those in a critical condition, Health Secretary Nicola Sturgeon said the rate of swine flu "hotspots" in Scotland, where two people recently died, was slowing and that five people remained in hospital with the virus.

In addition, 40 other victims have required hospital treatment since the outbreak in April.

Ms Sturgeon said: "In some areas, we are seeing a relatively large number of people going to the doctor with flu-like symptoms and, within that, there are likely to be new cases of H1N1.

"Nevertheless the Scotland-wide rate is not significantly higher than we would expect to see at this time of year.

"Furthermore, there are encouraging signs that rates of GP visits are declining in areas like Greater Glasgow and Clyde that have seen virus hotspots, suggesting that the spread may be slowing there."

But Lanarkshire has seen a rise in the number of people visiting GPs with flu-like symptoms according to statistics, which for the first time provide a rate for all flu-like illnesses - not necessarily H1N1 - for which a consultation has been sought.

The UK's chief medical officer, Sir Liam Donaldson, said the sharp rise in fatalities did not mean they all died directly from the virus, but he added that many of the victims had contracted it.

However, Sir Liam admitted that it was unknown how many people in the UK were actually suffering from the virus as many people would be treating themselves at home rather than contacting their GP.

It is unclear where or when the latest deaths linked to swine flu occurred.

He said that the latest information, from 100 GP surgeries around England, showed that around 27,000 people each week were being diagnosed with having a flu-like illness.

Of these, an estimated 8000 will have swine flu. By yesterday there were 9718 confirmed cases of swine flu in the UK. Mexico has around 10,000 cases and the US close to 34,000.

Sir Liam said yesterday that London and the West Midlands were approaching epidemic levels in terms of the number of cases being seen.

The number of cases is now being monitored in various ways including laboratory testing on sample groups, some GP practices and the number of calls received by NHS Direct.

However, Sir Liam acknowledged that the true number of people with swine flu was unknown.

He said: "We do know something about the people seeking help from the NHS but there will be many other people who look after themselves, don't realise they have it and don't show up.

"We have to acknowledge the problem is bigger than surveillance is showing us.

"That will always be the case, it would be the case with seasonal flu or anything else."

The Westminster government last week estimated that around 100,000 new cases of swine flu could occur in the UK by the end of August.

Sir Liam said that was the most accurate prediction to date of what will happen.