Speaking at BHP’s London AGM overnight, Nasser revealed that he planned to announce his retirement from the board last year.

“However, the board believed it was important that I continue on as chairman to provide stability as we responded to Samarco,” he said.

“Now that the basic structure of the Samarco response is in place, the findings of the expert panel have been published, the compensation and remediation programs have been initiated, and with BHP Billiton in robust shape, I have decided that I will not seek re-election at next year’s AGM.

“As you know, board renewal and succession planning is an ongoing process, including chairman succession, and is led by the board as a whole.

“Through this time, I will continue to lead the board as we optimise overall BHP Billiton performance.”

Nasser said, coming up to the one-year anniversary of the Samarco disaster, the past year had been one of the most challenging in BHP’s history.

“We contended with a range of difficult issues, none more serious than Samarco,” he said.

“We faced up to those issues, while also taking decisive actions to make our company safer and stronger for the long term.”

It comes as Brazil’s Prosecutors Office filed criminal charges against BHP and certain current and former employees.

It has been reported that 21 people, including former iron ore boss Jimmy Wilson, have been charged with qualified homicide over the November 2015 dam collapse that killed 19 people and left hundreds homeless.

BHP said this morning that it was yet to receive formal notification of the proceedings.

“BHP Billiton Brasil rejects outright the charges against the company and the affected individuals,” BHP said.

“We will defend the charges against the company, and fully support each of the affected individuals in their defence of the charges against them.”

BHP shares gained 1.7% yesterday to $A22.85.