International audienceThis article addresses the issue of favoritism at the design stage of a complex procurement auction. A community of citizens procures a project but lacks the ability to translate its preferences into operational technical specifications. This task is delegated to a public officer who may collude with one of the firms in exchange of a bribe. We investigate a simple accountability mechanism that requires justifying one aspect of the technical decision determined by the alerts of competitors (alert-based accountability [ABA]). We find that relying on competitors enables the community to deter favoritism significantly more easily than random challenges. The penalty needed to fully deter corruption is independent of the com...