Reference to responsible business conduct is becoming increasingly common within investment treaty law, including within bilateral trade agreements.
This trend is reflected within the latest EU-Singapore Free Trade Agreement which makes explicit reference to social responsibility practices and the OECD Guidelines for Multinational Enterprises:
”When promoting trade and investment, the Parties should make special efforts to
promote corporate social responsibility practices which are adopted on a voluntary
basis. In this regard, each Party shall refer to relevant internationally accepted
principles, standards or guidelines that it has agreed or acceded to, such as the
Organization for Economic Cooperation and Development Guidelines for
Multinational Enterprises, the UN Global Compact, and the ILO Tripartite Declaration
of Principles concerning Multinational Enterprises and Social Policy. The Parties
commit to exchanging information and cooperating on promoting corporate social
Full text of the agreement can be found here.
 For more information see Investment treaty law: sustainable development and responsible business conduct: A fact finding survey OECD, 2014; Information on OECD work on international investment law generally is available here.