This article shifts the analysis of parliamentary oversight tools to the level of the political party, asking how political parties make use of written parliamentary questions. It theorises that the use of parliamentary questions is related to the ideological and electoral competition between political parties, borrowing from theories on issue competition and negative campaigning. It provides an empirical test, using data on written questions from the lower house in the Netherlands (1994-2014). The analysis shows that parties tend to put questions to ministers whose portfolios are salient to them, in line with issue ownership theories. Moreover they ask questions of both ministers from parties that are ideologically distant and those with whom they have considerable electoral overlap in line with studies of negative campaigning.