Deaths caused by the hospital superbug Clostridium difficile have soared by more than 60 per cent in Scotland in a single year, according to shocking new figures.

The bug, whose spread has been linked to poor cleanliness in hospital wards, was the main cause of death of 164 people last year - up from 100 in 2005. C difficile was also a contributing factor in the deaths of a further 253 people, statistics from the General Register Office for Scotland revealed.

Experts warned the bug appeared to be becoming more virulent and called for better hygiene in hospitals to tackle it. Opposition politicians described the statistics as "alarming".

The figures come after hospitals in Kent were condemned in an official report for appalling hygiene standards that enabled C difficile to kill 90 people.

Dr Ian Gould, a consultant microbiologist at Aberdeen Royal Infirmary, said: "There definitely is a real increase in the virulence of some strains. Dealing with C difficile is complicated, but much of it is the same as with MRSA. We are trying to improve the use of antibiotics to control the infection.

"We need to improve hand hygiene and the hygiene of healthcare staff. We also need to look at bed occupancy and the space between beds to stop it spreading. But there is also a need to get a better understanding of C difficile, as there is a lot we still don't know at the moment."

However, he said that increased testing might also be playing a part in pushing up the C difficile figures.

While the bug is present in the stomachs of about 3 per cent of the population, it is the use of certain antibiotics in hospital that can allow it to develop into a serious and potentially fatal infection. Once one patient is infected, it can easily be spread to others on the same ward.

C difficile causes severe diarrhoea and other complications, and is a particular threat to the frail and elderly.

Figures obtained under Freedom of Information laws by The Scotsman earlier this year revealed that the number of cases in Scotland was much higher than previous estimates had suggested.

Figures from Health Protection Scotland indicated there could be as many as 6,000 cases of C difficile-related disease each year among the over-65s.

It is not just in Scotland where the problem is getting more serious. Figures from the Office for National Statistics show that in England and Wales in 2005 there were 2,074 cases where C difficile was mentioned as the main cause of death - up by 67 per cent on the 1,245 cases seen in 2004. The statistics for 2006 have yet to be released.

Dr Robbie Robertson, from the Scottish Patients' Association, said the rising number of deaths linked to C difficile would increase anxiety among patients going into hospital.

"They are very worried about these infections," he said. "Before C difficile, it was MRSA which was causing them concern, and still is. These are very serious infections, particularly among the most vulnerable and frail patients."

Dr Robertson said hygiene was very important in controlling C difficile.

"There is evidence that these spores can spread around the hospital and affect other people," he said. "Hygiene is crucial and should be strictly observed on hospital wards.

"We also have to be wary of hospital overcrowding, which can cause it to spread more easily between patients. And staffing levels are also important because, if you have nurses who are run off their feet, they will be forced to take short cuts."

Ross Finnie, the Liberal Democrats' health spokesman, said: "These figures are extremely alarming and point to serious management failure. I urge the Scottish Government to ensure that the systems to combat hospital-acquired infections are also effective against new and growing infections such as C difficile."

Mary Scanlon, the health spokeswoman for the Scottish Conservatives, agreed that the increase in C difficile deaths was "very alarming". She said: "While most of the attention has so far been on MRSA, we seem to have been unaware of the huge increase in C difficile."

She went on: " A hospital has become a hazardous place as opposed to a hygienic place for care and treatment, and patients are now more worried about getting these infections than they are about having surgery.

"It is quite obvious that measures that have been brought in to combat healthcare-associated infections are simply not enough and they are not working. The Scottish Government must ensure that health boards are putting in place quality standards on hygiene and infection control."

But Margaret Curran, the shadow health secretary, said because of Labour's commitment in office to tackling hospital-acquired infections, Scotland was among "the top three successful nations in the world at addressing this challenge". "It is disappointing that the SNP have said so little about this," she said.

Nicola Sturgeon, the health secretary, said: "C difficile is recognised nationally and internationally as an increasing problem, both in hospitals and in the community. While at least some of the increase in reporting of C difficile on death certificates will be due to increasing awareness and profile of this infection, it is clearly a serious issue. That is why the Scottish Government is addressing healthcare-associated infections on a number of different fronts."

Alistair Leanord, the director of Scottish Infection Research Network, said there was still a "massive amount" still unknown about C difficile.

"Although C difficile has been with us a long time, I would still class it as an emerging disease because we are still learning more about it and it is becoming more prominent," he said.

He added that research was now focusing on both the infection itself and the genes that might make people more likely to develop the disease. "Researchers are looking at whether there is a genetic predisposition to C difficile, and if we find what it is, that could alert us to patients who will face a greater risk."

But Dr Leanord said it could be five or ten years before major new breakthroughs could be found to combat C difficile. In the meantime, he said infection control and good hygiene remained "the bread and butter" in cutting cases of C difficile in hospitals. "This is very basic stuff, but it is stuff that will help make a difference," he said.

- Two hospital wards were closed to new admissions yesterday after five patients were found to be carrying MRSA. A medical ward at the Southern General Hospital in Glasgow is treating three patients for MRSA, none of whom are giving any cause for concern

And the intensive therapy unit at Inverclyde Royal Hospital has two patients being treated for MRSA. Patients who would normally be admitted to the unit are being transferred to other units in nearby hospitals.

Q & A: THE BUG

What is Clostridium difficile?

C difficile is a bacteria which is present in the gut of up to 3 per cent of healthy adults without causing any problems. Babies and the elderly are most at risk from developing illnesses linked to the bacteria.

How do you catch C difficile?

The use of certain antibiotics can disturb the normal bacteria in the stomach, making it more likely that C difficile can take over and cause illness. Once someone has the infection, it is possible that spores from their diarrhoea can spread and infect other patients, especially where good infection control measures are not in place. The spores can survive for a long time in the environment and spread on the hands of health staff who touch contaminated items.

What are the symptoms of C difficile?

Some people may suffer no effects from carrying C difficile. But those who do develop disease related to the bug can suffer severe diarrhoea and sometimes severe inflammation of the bowel. Other symptoms include fever, loss of appetite, and stomach pain and tenderness.

How can the infection be treated?

Doctors can treat C difficile by using certain antibiotics which do not allow it to grow in the gut. Patients may also be given pro-biotic treatments to re-balance the "gut flora".

Is C difficile always fatal?

Most people who suffer diarrhoea as a result of C difficile will make a full recovery. But elderly patients with other underlying illnesses face a greater risk.

How can we prevent the spread of C difficile?

Patients in hospital and those on antibiotics are most likely to fall ill with C difficile. To reduce the risks of it spreading, people should wash their hands with soap and water - alcohol gels are not effective in killing all the bacteria.

What are hospitals doing to try to stop C difficile?

Good hygiene is key to reducing the spread of the bug, as are good antibiotic prescribing practices. Staff should make sure areas around infected patients are rigorously cleaned. Isolating infected patients and making sure there is adequate space between hospital beds is also important.