The legitimacy of the Group of 20 (G20) is frequently challenged: the group has been criticised by non-member states, non-governmental organisations (NGOs) and in both the scientific and broader public debate with regard to the content and effectiveness of its policy measures and its limited membership structure. Accountability mechanisms can attenuate these shortcomings in different ways: they can increase the capacity of the citizens of the member states to surveil the activities of the G20 and can form the basis of learning processes within the group so as to increase effectiveness. In addition, accountability mechanisms directed towards non-member states can make the G20 more receptive to the interests of people who do not live in its own countries but are nevertheless affected by the policies of the G20. In this paper we analyse the existing accountability mechanisms of the G20 and discuss the challenges that the adoption of the 2030 Agenda for Sustainable Development as a guiding framework for G20 work poses to them. While the G20 also constitutes a platform for the reciprocal accountability of its individual member countries, our focus lies on the accountability mechanisms of the institution of the G20 as a whole. Based on the literature, we can identify three elements of accountability: transparency, justification, and enforcement. The institutionalised accountability mechanisms of the G20 are primarily directed at the first two elements of accountability, as the G20 ¬¬¬– like all club governance institutions is not subject to any formal sanctioning mechanisms. However, besides being valuable in their own right, transparency and justification make weaker forms of sanctions such as criticism by independent agents as well as reputational effects possible. The most prominent accountability mechanisms of the G20 are its interaction with the media; the publication of accountability reports; and a dialogue process with the so-called Engagement Groups from civil society, business, and academia. In the end, these mechanisms are intended to render the G20 accountable to the citizens within and outside G20 countries (either directly, or mediated by other agents). At the same time, however, they sometimes also fulfil an additional function for the G20 itself, namely tracking its own work towards its commitment to learn from past experiences.

In 2015, the international community adopted the 2030 Agenda for Sustainable Development as a universal development agenda. The G20 assumed the principles of the 2030 Agenda and a special responsibility for its implementation through its 2016 G20 Action Plan on the 2030 Agenda for Sustainable Development. Thereby, new challenges for accountability in the G20 have arisen.

When looking towards the future, several suggestions for the G20 can be raised in order to increase its accountability, particularly in light of the demands set by its role in the implementation of the 2030 Agenda. To increase the credibility of its accountability processes, it is necessary to allow for more independent evaluation. For this to be possible, the work of the G20 must become first and foremost more transparent. Possible ways to achieve this range from the establishment of a permanent website, over allowing selected civil society members to attend its working group meetings, to publishing agendas, minutes and issue notes. Self-reports should best be concentrated on descriptions rather than selfevaluation. In order to allow for coherent reporting on the 2030 Agenda, one central report should overarchingly cover all relevant G20 actions in the so-called Sustainable Development Sectors (SDSs) of the G20 Action Plan on the 2030 Agenda for Sustainable Development (and its 2017 Hamburg Update). Comprehensive reporting on joint actions taken by the G20 could complement the United Nations follow-up process for individual countries. If given sufficient access to the relevant information, Engagement Groups such as the T20 (Think 20) could play a vital role in providing credible and informed independent evaluation of G20 policies. This would be a particularly promising way forward in the context of the 2030 Agenda, as the agenda will require common efforts by both policymakers and society for its successful implementation. Improving on its existing system of accountability mechanisms cannot fully compensate for the lack of legitimacy that is associated with the exclusionary institutional set-up of the G20. Yet establishing “streamlined, coherent, and credible” accountability processes (G20, 2016, p. 15) could prove to be a key element in addressing its legitimacy problems.