OBJECTIVE: To examine socio-economic inequalities in decreases in household sugar purchasing in Great Britain (GB). DESIGN: Longitudinal, population-based study. SETTING: Data were obtained from the GB Kantar Fast-Moving Consumer Goods (FMCG) panel (2014-2017), a nationally representative panel study of food and beverages bought and brought into the home. We estimated changes in daily sugar purchases by occupational social grade from twenty-three food groups, using generalised estimating equations (household-level clustering). PARTICIPANTS: British households who regularly reported food and beverages to the GB Kantar FMCG (n 28 033). RESULTS: We found that lower social grades obtained a lower proportion of sugar from healthier foods and a greater proportion of sugar from less healthy foods and beverages. In 2014, differences in daily sugar purchased between the lowest and the highest social grades were 3·9 g/capita/d (95 % CI 2·9, 4·8) for table sugar, 2·4 g (95 % CI 1·8, 3·1) for sugar-sweetened beverages, 2·2 g (95 % CI 1·5, 2·8) for chocolate and confectionery and 1·0 g (95 % CI 0·7, 1·3) for biscuits. Conversely, the lowest social grade purchased less sugar from fruits (2·1 g (95 % CI 1·5, 2·8)) and vegetables (0·7 g (95 % CI 0·5, 0·8)) than the highest social grade. We found little evidence of change in social grade differences between 2014 and 2017. These results suggest that recent overall declines in sugar purchases are largely equally distributed across socio-economic groups. CONCLUSIONS: This suggests that recent population-level policy activity to reduce sugar consumption in GB does not appear to exacerbate or reduce existing socio-economic inequalities in sugar purchasing. Low agency, population-level policies may be the best solution to improving population diet without increasing inequalities.