Inappropriate prescribing in primary care was implicated in nearly half of asthma deaths reviewed in the UK's recent National Review of Asthma Deaths. Using anonymised EMIS-Web data for 139 ethnically diverse general practices (total population 942,511) extracted from the North and East London Commissioning Support Unit, which holds hospital Secondary Uses Services (SUS)-linked data, we examined the prevalence of over-prescribing of short-acting β2-agonist inhalers (SABA), under-prescribing of inhaled corticosteroid (ICS) inhalers and solo prescribing of long-acting β2-agonists (LABA) to assess the risk of hospitalisation for people with asthma for 1 year ending August 2015. In a total asthma population of 35,864, multivariate analyses in adults showed that the risk of admission increased with greater prescription of SABA inhalers above a baseline of 1-3 (4-12 SABA: odds ratio (OR) 1.71; 95% confidence interval (CI) 1.20-2.46, ⩾13 SABA: OR 3.22; 95% CI 2.04-5.07) with increasing British Thoracic Society step (Step 3: OR 2.90; 95% CI 1.79-4.69, Step 4/5: OR 9.42; 95% CI 5.27-16.84), and among Black (OR 2.30; 95% CI 1.64-3.23) and south Asian adult populations (OR 1.83; 95% CI 1.36-2.47). Results in children were similar, but risk of hospitalisation was not related to ethnic group. There is a progressive risk of hospital admission associated with the prescription of more than three SABA inhalers a year. Adults (but not children) from Black and South Asian groups are at an increased risk of admission. Further work is needed to target care for these at-risk groups.