Supermarket shoppers who buy lots of foods on “two for one” deals are far more likely to be obese, a major study suggests.

Cancer Research UK found that those with highest consumption of discounted foods were at 50 per cent greater risk of obesity, compared with those with low take-up of such deals.

The study of more than 16,000 households found almost one in three food and drink items in UK supermarket baskets were bought on promotion.

And the discounts were far more likely to be applied to unhealthy foods, with almost half of all chocolate, crisps, popcorn, and savoury snacks are being bought on promotion.

Shoppers whose baskets contained between 40 and 80 per cent of goods on special offer were 54 per cent more likely to be obese than those with a maximum 20 per cent of foods on such deals.

Those with highest take-up of the deals bought 30 per cent less fruit, and nearly 25 per cent fewer vegetables than those shunning deals.

The study follows a Government consultation on proposals to ban “buy one, get one free” deals on unhealthy foods and supermarket “guilt lanes” as part of its childhood obesity strategy.