More people in the UK have severe asthma than anywhere else in the world, experts have found.
Millions of British children have asthma
The Global Initiative for Asthma (Gina) report found Scotland is worst affected, with more than 18% of people experiencing symptoms.
Almost 17% of children and adults in Wales and 15.3% of those in England also suffer from the condition.
In Switzerland, just 2.3% of the population is affected by asthma, while in Greece the figure is 1.9%.
The Gina report says almost a third of children aged 13 and 14 in Scotland, Wales and England report experiencing asthma symptoms - more than anywhere else in the world.
And a quarter of UK adults are affected by asthma to some degree - double the number in France and nearly three times the number of Italian adults with the disease.
The report draws together information on asthma from across the world, giving experts comprehensive information about how the disease is affecting countries.
It says asthma places a huge burden on the UK's health service, with GPs seeing 20,000 new cases of the disease each week.
Asthma is linked to 75,000 emergency hospital admissions and approximately 1,500 deaths each year.
But experts say many patients are currently suffering more than they need to with their disease because they are not receiving the right treatment.
Professor Eric Bateman, chairman of the Gina scientific committee, said: "This report demonstrates that we are failing to achieve the established global guidelines, which state that the goal of asthma therapy should be near, or complete, freedom from asthma symptoms.
"We now have treatments that can help prevent and control symptoms, but a lot of patients do not understand that they have to take them regularly.
"This lack of education results in an over reliance on short-term reliever medications which are only taken after symptoms have appeared."
Professor Martyn Partridge, chief medical adviser to the National Asthma Campaign, said: "With such a large number of people with asthma it is essential that they receive the best possible care.
"That care should include prompt and accurate diagnosis and then the patient needs to acquire the skills needed to control their own condition.
"Self-management education is rarely offered in the UK despite overwhelming evidence that it reduces suffering associated with this common condition."
Asthma experts say much more research needs to be carried out into what triggers asthma, and why the numbers affected are increasing.
Dr Chris Griffiths, of the Barts and the Royal London Hospitals, said: "It may be that something is switching asthma on in susceptible individuals, probably in the first few years of life.
"There are a range of suspects. It could be outdoor pollution, smoking, the diet, the way we seal ourselves in our houses more.
"There is no one factor, it is going to be a combination of things."