Traffic pollution has been blamed for causing asthma
The National Asthma Campaign (NAC) estimates that 5.1m people - 1 in 13 adults and 1 in 8 children - are currently being treated for the condition.
Last time the charity carried out similar research in June 1999 the figure was 3.4m.
Nobody knows why asthma is becoming more common, but it is thought to be due to a complex combination of genetic and environmental factors.
A rise in pollution has been blamed, but there is no conclusive proof. Another theory is that an unhealthy diet plays a role with too many additives and not enough fresh fruit and vegetables.
It is thought that the most important trigger is viral infection.
The results of the NAC audit also indicate that serious asthma is responsible for 74,000 A&E admissions every year. In many cases patients' lives are under threat.
The NAC is calling for improved care for asthma patients to reduce the need for emergency hospital admission.
It says that GP surgeries should regularly monitor all people at risk of serious attack.
If a patient does require hospital admission, says the NAC, then they should always be seen by an specialist in the field.
Professor Duncan Geddes, an expert in respiratory medicine at the Royal Brompton Hospital, said: "In many cases, emergency treatment could be avoided, but sometimes, an emergency admission is the only way that vulnerable people are identified by the health care system.
"We must ensure that this unfortunate opportunity is used to the advantage of the person with asthma - and that they are given the care they obviously need."
New cases
The NAC audit found that the number of new cases of asthma each year is now three to four times higher in
adults and six times higher in children than it was 25 years ago.
In 2000, GPs in the UK saw over 18,000 cases relating to new asthma attacks each week.
Currently 1,500 people still die from asthma each year, over a third of which are people under the age of 65.
It is thought that many of these deaths might have been prevented with adequate routine and emergency care.
GP surgeries are responsible for organising treatment for most people with asthma.
But the NAC found many people do not receive adequate information or advice when asthma is first diagnosed.
Very few people with asthma have a written self-management plan explaining when to take medication (6%) or what to do if asthma worsens (3%).