Smoking a shisha pipe is as bad for people as smoking tobacco, the Department of Health and the Tobacco Control Collaborating Centre has found.
People who smoke shisha, or herbal tobacco, can suffer from high carbon monoxide levels, its research revealed.
It found one session of smoking shisha resulted in carbon monoxide levels at least four to five times higher than the amount produced by one cigarette.
High levels of carbon monoxide can lead to brain damage and unconsciousness.
Shisha is a water-pipe, popular in many Arab countries, in which fruit-scented tobacco is burnt using coal, passed through an ornate water vessel and inhaled through a hose.
The Department of Health said it was difficult to know exactly how much carbon monoxide one cigarette produced, due to the differences in smokers' inhalations.
But measuring carbon monoxide in exhaled breath showed a normal non-smoker's level to be three parts CO per million parts of air (ppm) (less than 1% of blood not working properly), a light smoker to have 10-20 ppm (2-4% of blood not working properly), and a heavy smoker 30-40 ppm (5-7%).
The study found shisha smokers had 40-70 ppm of CO in their breath - affecting 8-12% of their blood.
Dr Hilary Wareing, director of the Tobacco Control Collaborating Centre, told the BBC's Asian Network she was shocked by the results of the research.
"Our mouths opened at the level of harm - none of the tests we did showed anything other than shisha is hazardous to health."
Paul Hooper, regional manager at the Department of Health, said the findings made the dangers of shisha a "major issue".
He said many people regard shisha "as not even smoking".
Shisha bars, which are typically decked out with low stools and soft cushions to create an inviting atmosphere, have become popular in cities across the UK, particularly in London, Manchester and Birmingham.
An activity largely associated with Middle Eastern customers and a young crowd, there is a growing trend of themed shisha parties.
Many people who go to "shisha evenings" think it is a safer alternative to smoking cigarettes.
"You never see it in the news - 'that is terrible, don't do it' - there's no shock tactics like (there is with) cigarettes," said one young woman.
"If my mum sees me smoking shisha, she isn't going to take it as seriously as if I was smoking cigarettes," said a British Pakistani man.
It was this misconception - and finding dangerous levels of carbon monoxide in a pregnant woman who had stopped smoking tobacco, but continued to smoke shisha - which prompted the research.
"We found one session of smoking shisha - that's 10 milligrams (of fruit tobacco) for 30 minutes - gave carbon monoxide levels that were at the lowest four and five times higher than having a cigarette," said Dr Wareing.
"But at the worst, shisha was 400 to 450 times more dangerous than having a cigarette," she added.
Shisha smokers in a cafe in Edgware Road, London, said the findings would make them think twice about smoking.
"You know you can die from cigarettes, but you don't know you can die from shisha," said one.
"I'm now going home to research it," said another.
But not everyone is convinced.
Akram, a 27-year-old who runs a restaurant and shisha bar in Birmingham, has his own views.
"There is a health risk but it's all down to consumption and all the evidence I've seen is that smoking shisha is nothing like smoking even one cigarette," he said.
He said he did not actually inhale shisha smoke.
It is not just the level of carbon monoxide that is causing concern.
Qasim Choudhory, a youth worker at the NHS Stop Smoking Service in Leicester, said sharing a shisha pipe could pass around infections.
"There's a heightened risk of getting TB, herpes and infections like that," she said.
"Now you know swine flu is on the top of the agenda right now - there's no kind of direct correlation, but at time when we're up on our hygiene, it's not the best type of activity to be taking part in."
Dr Wareing said more research on exactly how dangerous shisha was needed to be conducted to enable people to make an informed choice.
Paul Hooper said the department was working hard at "how best to get the message - that it is dangerous - across to the consumer".
"But how do you label the tobacco and the shisha pipe? It's not as simple as labelling a packet of cigarettes," he added.
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