The topic of the here presented work is the influence of firms on climate policy. This thesis analyses the impact of firms’ influence on the acceptance of climate policy, its effectiveness, and implementation. Hereby, the mediation of private interest is understood as social barrier on the design and implementation of effective climate policy. The work is empiric, dealing with the features of Swiss and European climate policy in two case studies. The thesis follows an interdisciplinary approach combining theories from economics, business strategy and political sciences. In a mixed‐ methods approach, it analyses the positions of the business community on climate policy, the different channels of interest group influence and the impact on policy output. Thereby, the focus of the analysis is on the positions and interactions between business interest associations and political decision‐makers. The results show that there is a pluralist picture of firms’ positions on climate policy. According to their economic short‐term interests, firms tend to block or defend the detailed features of climate legislation. By contrast, business associations have an incentive to exaggerate their stated positions strategically, which questions the reliability of their positions in the process of political consultation. The analysis shows further that private interest is asymmetrically represented in the political decision‐making process. In Switzerland, a small group of private actors enjoys privileged access to policy‐makers on the expense of public interests. This influence by special interest groups impedes effective policymaking and causes a democracy‐deficit. As a result, interest group influence inhibits effective decision‐making, which reduces societal welfare. Furthermore, a comparative case study on self‐regulation of the European and Swiss automotive industry demonstrates that there is a trade‐off between acceptance and environmental effectiveness in climate policy design. The work concludes that a fair stakeholder dialogue, the dissemination of knowledge, transparency in political decision‐making, and the integration of scientific expertise should be enhanced for ensuring effective implementation of politically acceptable and environmentally effective climate policies and measures.