Barclays Bank is facing a formal complaint over its financial links to a coal-fired power station near the Sundarbans, the world’s largest mangrove forest and home to millions of people in Bangladesh and India.

Three complainants from the region have submitted a case to the UK government’s Office for Responsible Business Conduct, alleging that the British bank breached international guidelines by underwriting companies involved in the emission-heavy Maitree super thermal power project, also known as the Rampal power plant.