More than 600,000 Brazilians, 46 local governments and around 2000 businesses are suing BHP over the 2015 collapse of the Mariana dam in southeastern Brazil, which was owned and operated by BHP and Vale's Samarco joint venture.
The dam's collapse unleashed a wave of toxic sludge that killed 19 people, left thousands homeless, flooded forests and polluted the length of the Doce River.
A tsunami of toxic mud, caused by the dam break, engulfed a town in Brazil, killing 19. (AP PHOTO)
The claimants' lawyers accused BHP of "cynically and doggedly" trying to avoid responsibility as the trial of a lawsuit worth up to 36 billion pounds ($A70 billion), one of the largest in English legal history, began on Monday.
They also allege BHP contributed to the collapse of the dam by allowing it to be raised as part of an expansion project, despite an increasing risk of failure.
BHP, the world's biggest miner by market value, is contesting liability and says the London lawsuit duplicates legal proceedings and reparation and repair programmes in Brazil and should be thrown out.
The miner argues it did not own or operate the dam, which held mining waste known as tailings, and that Samarco operated independently. It also says it had no knowledge the dam's stability was compromised before it collapsed.
BHP's lawyer Shaheed Fatima told the court on Wednesday that the case against it was fundamentally flawed.
Thousands were left homeless after the dam collapsed and a wave of toxic sludge engulfed a town. (AP PHOTO)
"The claimants appear to say that BHP was so motivated to make profits from their investment in Samarco that they got behind the wheel, they operated the business, they put profits before safety," she said.
"This is unrealistic and illogical."
"The profits before safety allegation, that is particularly far-fetched and unjustified."
She said that BHP's former finance chief Peter Beaven, who is due to give evidence next month, said in a witness statement: "BHP had a culture which was embedded throughout the organisation from top to bottom of safety before anything else."
The ongoing 12-week trial to determine whether BHP is liable to the claimants comes as the Brazilian authorities' negotiations with BHP, Vale and Samarco over a nearly $US30 billion ($A45 billion) compensation deal continue.
Sources close to the negotiations told Reuters a final agreement could have an impact on the London lawsuit, a suggestion the claimants' law firm Pogust Goodhead rejected.
