Existing literature on international migration suggests that partisan differences exist in regards to policies that regulate the conditions of migrants residing in host countries (migrant policies), but not in regards to policies determining the admission of new migrants (migration policies). We propose that partisan differences exist regarding migration policies, but that these differences are conditional on a party-labor relationship. In our empirical analysis, we use error correction models to examine asylum and labor migration policies in Western European countries from 1984 to 2006. We find that migration policies become more liberal as government partisanship moves to the left only when unskilled manual workers split their votes between left-wing and right-wing parties. The result implies that a strong relationship between left-wing parties and workers, which mutually benefits both groups in some areas (such as welfare), may be incompatible when conflicts arise between their interests concerning issues such as international migration.