**Abstract** In this study, we examine whether welfare deservingness judgements in the UK are affected by a bias against claimants from stigmatised social class backgrounds. In the UK, as in other countries, stereotypes of a perceived social ‘underclass’ are widespread. Political and media discourse frequently portrays members of this ‘underclass’ as lazy, feckless, and not genuinely in need of support. Yet despite strong academic interest in perceived welfare deservingness, existing research has largely neglected the role of social class bias in deservingness judgements. To address this gap, we use a novel vignette experiment administered to a representative sample of British respondents to provide the first direct evidence of discrimination against welfare claimants with ‘underclass signifiers’. We find that the British public are more likely to endorse a sanction against a claimant from an ‘underclass’ background than against an otherwise identical claimant from a less stigmatised class background. We also asked respondents to justify their decisions and, applying computational methods to analyse these free-text responses, we find that ‘underclass’ claimants are more likely to be blamed for violating the conditions of their benefit, while claimants from other class backgrounds are more often given the ‘benefit of the doubt’. Our findings have important implications for our understanding of the relationship between social class background and public deservingness perceptions, and potentially for the differential treatment of claimants by the benefits system. **NOTES** There are two sets of files attached to this project which can be used to reproduce the results reported under H1 and H2 in the paper. The first set of files includes the data and code (in Stata format) used to produce the results reported under H1 (SPASanctionsVignette_OSFCODE, and SPASanctionsVignette_OSFDATA. The second set of files includes the data (in csv format) and code (R script) for conducting the STM analysis reported under H2 (SPASanctionsVignette_STMCODE, and SPASanctionsVignette_CSVDATA. If you have any questions about the data or code, please contact the paper's corresponding author Robert de Vries (r.devries@kent.ac.uk)