This thesis investigates the relationship between transnational interest groups, The United Kingdom (UK) and The European Union (EU) on the issue area of climate change. It finds evidence to suggest that meaningful integration is taking place in Europe in environmental issue areas particularly that of climate change. Further, it finds that this integration has taken place in large part due to the efforts of transnational sub-state actors and supranational bureaucrats at the EU, recommending a neo-functionalist interpretation of UK/EU relations in the area of climate change.