Victims of Brazil’s worst environmental disaster have written to the British prime minister, Rishi Sunak, accusing the mining company BHP of “environmental racism” and urging the UK government to act on unethical practices by British companies. About 720,000 Brazilians are suing BHP, an Anglo-Australian company that until recently had its headquarters in London, over its role in the 2015 Mariana dam disaster. The company denies liability. It is facing claims for compensation amounting to £36bn in the world’s largest group claim in English legal history. In November 2015, the Fundão tailings dam, which BHP co-owned with the Brazilian iron ore producer Vale, burst. It unleashed 60m cubic metres of toxic waste, which obliterated land below and polluted everything in its path for more than 600km. The waste killed 19 people, buried villages, made thousands homeless and affected the livelihoods of hundreds of thousands more. The impact continues to wreak havoc on the ecosystem and environment, as well as on people’s health. “We believe BHP is guilty of environmental racism,” said the letter, delivered to 10 Downing Street on Thursday by some of those affected. “It is our Indigenous communities who have been most affected by the disaster; our communities who were most at risk from mining activities; and our communities that continue to be denied justice by BHP.” A spokesman for BHP said the company “strongly refutes any accusations of environmental racism”. In Brazil, BHP, along with Vale, and Samarco, the joint venture company responsible for managing the Fundão dam, established the Renova Foundation to provide compensation for individuals and some businesses for loss and damages, as well as mitigating the disaster’s environmental impacts. It has funded more than $6bn (£4.58bn) of rehousing, rehabilitation and indemnification for all communities affected by the disaster, he added. The issue was discussed in British parliament last month. Tan Dhesi, the Labour MP for Slough, said: “Companies running large operations worldwide cannot be allowed to hide behind their subsidiaries when things go wrong or when there is an ecological and environmental disaster. The UK has an important global role.” Jim Shannon, a DUP MP, told those present: “I cannot help but feel that if British or Australian communities had been impacted by such a disaster, they would not have been treated in the same way. Indeed, it would have been sorted a long time ago.” The letter asks the UK government to recognise its “vital role in stopping such disasters ever happening again” and to “crackdown on British companies that fail to live up to their social and environmental credentials at home and abroad”. Tom Goodhead, the global managing partner and chief executive of Pogust Goodhead, the London-based international law firm representing the victims, said: “This is not about money for most of these people – they want justice.” Meanwhile, BHP and Vale are embroiled in a legal battle over which has legal and financial responsibility for the disaster. Goodhead added: “They are wasting time, energy and resources instead of sitting down with the victims and solving this case. They refuse to face up to the consequences of their negligence. It’s a disgraceful spectacle.”