More than a quarter (28%) of Sainsbury customers said they would turn to discounters if they had less money in their pockets. This compares with 18% of Morrisons' shoppers and 11% of both Tesco and Asda customers.
The surprising findings show the importance of Sainsbury's relaunch of value brand Basics last year, intended to show that it could deliver competitive prices. However, the retailer needs to work hard to communicate the quality of this offer.
IGD Consumer Unit's Shopper Attitudes to Value Retailing research finds that the multiple's customers have the least positive perception of retailer budget brands, with 31% saying they had been disappointed in the past and 30% having poor expectations of the brand.
Only 18% of Sainsbury customers believe budget brands are as good as manufacturers' brands, compared with a quarter of Tesco customers and 28% of Asda and Morrisons shoppers.
"Sainsbury will need to remain price competitive and ensure a strong offer in its relaunched Basics range to retain its less affluent shoppers," said IGD senior business analyst and report author Jules Stark.
The findings also show that the hard discounters, such as Aldi, Lidl and Netto, could attract the more affluent Sainsbury shoppers if they targeted them with an offer that met their needs. The challenge is to attract them when they have money in their pockets - possibly by stocking more brands to dispel the perception of low quality.
Some 41% of shoppers who would buy more budget brands live in southern England, according to the research, while 41% are men and 39% married.
Tesco shoppers are most likely to buy certain retail budget products, possibly thanks to the reputation of Tesco Value, says IGD. "Traditional brands will need to work harder to capture shopper spend by communicating their point of difference and justifying their price premium," said Stark.