The paper presents the method and findings of a Delphi expert survey to assess the impact of UK government farm animal welfare policy, farm assurance schemes and major food retailer specifications on the welfare of animals on farms. Two case-study livestock production systems are considered, dairy and cage egg production. The method identifies how well the various standards perform in terms of their effects on a number of key farm animal welfare variables, and provides estimates of the impact of the three types of standard on the welfare of animals on farms, taking account of producer compliance. The study highlights that there remains considerable scope for government policy, together with farm assurance schemes, to improve the welfare of farm animals by introducing standards that address key factors affecting animal welfare and by increasing compliance of livestock producers. There is a need for more comprehensive, regular and random surveys of on-farm welfare to monitor compliance with welfare standards (legislation and welfare codes) and the welfare of farm animals over time, and a need to collect farm data on the costs of compliance with standards.