When Legislators Do Not Differentiate: A Field Experiment on British MPs’ Responses to Constituent Policy Queries

How do legislators respond to constituent policy queries? Existing research suggests that legislators vary their responsiveness and tailor response content depending on constituent congruence, raising normative concerns about legislator–constituent communication. We report results from a pre-registered audit study of UK MPs which is the first to test whether legislators in party-centred parliamentary democracies vary substantive response rates and content depending on constituent–party policy congruence. We theorise that electoral incentives lead MPs to respond more to congruent constituents, and to place more emphasis on self over party when doing so. Our audit study uses real constituents as confederates, allowing better measurement of substantive responses. We find little evidence that constituent–party congruence affects MPs’ responsiveness or the personal versus party emphasis of their replies. These null findings refine understanding of legislator behaviour in parliamentary systems and are normatively encouraging regarding the role that legislator–constituent policy communications can play in parliamentary democracies.