Since the beginning of 2015 the British Conservative Party has used an online database called Votesource which is a centrally held database that local activists administer. The database merges both the membership database and the electoral roll and the centralised nature of it means the party can build demographic models based on Mosaic in to it to identify voters who are more likely to support the party at an election. The system is not without criticism and faced particular problems during the 2015 General Election and the primary to select the Conservative candidate for 2016 London Mayoral Election. A similar system with a similar Mosaic-based demographic model was used by Britain Stronger in Europe during the 2016 EU referendum.