From the longer Wikipedia page  which gives a list of members.
The Ethical Tea Partnership is a not-for-profit membership organisation that has been working with tea producers and tea companies to improve the sustainability of the tea industry since 1997. This industry-wide initiative, which was originally called the Tea Sourcing Partnership, was established by a number of large UK tea packing companies who took the decision to work together to improve the social conditions in their supply chains. Later on, ETP membership opened up to non UK based-tea packers, and extended the scheme to include environmental issues as well.
The ETP works in all the main tea producing regions and has a London-based Secretariat, and 5 Regional Managers based in Kenya, India, Indonesia, Sri Lanka and China. It runs three coordinated programmes to achieve its vision of a "thriving tea industry that is socially just and environmentally sustainable.
The website is