Apostcode lottery means fewer than two per cent of asthma patients in parts of the country are offered potentially life-saving drug treatments.
Experts say this is because many GPs are not aware of the injections, so they do not refer patients to specialists.
The injections – called biologics – cut the number of hospitalisations and mean severe asthmatics do not have to rely on inhalers.
But new research shows that fewer than 16 per cent of eligible asthma patients have been offered the drugs.
At this rate, it would take until 2061 for just half of those who need biologics to access them.
Nearly a third of eligible patients in Derby have been able to get a biologic prescription, but fewer than two per cent in Frimley, Surrey, have benefited.
Experts are calling on the NHS to ensure equal access to the crucial asthma medicine nationwide.