The billionaire investor Warren Buffett said on Wednesday that he is resigning as a trustee of the Bill and Melinda Gates Foundation and that he has donated half his wealth to philanthropy since pledging 15 years ago to give away his fortune gained from running Berkshire Hathaway.
Mr Buffett, 90, said he has been an "inactive trustee" for years at the foundation, but fully supported its chief executive, Mark Suzman, and that their goals were "100 per cent in sync".
He also announced a new $4.1 billion donation of Berkshire shares to the Gates Foundation and four family charities, part of his 2006 pledge to give away about 99 per cent of his net worth.
The future of the Gates Foundation has been uncertain following last month's announcement that co-founders Bill Gates and Melinda French Gates were divorcing after 27 years of marriage.
Founded in 2000, the non-profit focuses on combating poverty, disease and inequity, spending $54.8bn on such projects in its first two decades. It receives roughly four fifths of Mr Buffett's annual charitable donations.
The foundation did not immediately respond to a request for comment.
Mr Buffett did not mention the Gates's divorce as a reason for his resignation, noting he has also given up all directorships outside Berkshire, reducing his workload.
Arguably the world's most famous investor, Mr Buffett has since 1965 built Berkshire into a more than $600bn conglomerate, taking on businesses such as the BNSF railroad and Geico auto insurance, and stocks such as Apple.
"Over many decades, I have accumulated an almost incomprehensible sum simply by doing what I love to do," Mr Buffett said. "Society has a use for my money; I don't."
Wednesday's donations also go to the Susan Thompson Buffett Foundation, named after Mr Buffett's late first wife, and charities run by his children Howard, Susan and Peter: the Howard G Buffett Foundation, the Sherwood Foundation and the Novo Foundation.
Mr Buffett has assured his children they would still be taken care of.
"A very rich person should leave his kids enough to do anything, but not enough to do nothing," he told Fortune magazine in 2006.
Had Mr Buffett not made his donations, his fortune would roughly equal that of Amazon founder Jeff Bezos, the world's richest person, according to Forbes magazine.
Mr Gates and Mr Buffett also pioneered "The Giving Pledge", through which more than 200 people, including Michael Bloomberg, Larry Ellison, Carl Icahn, Elon Musk and Mark Zuckerberg, committed at least half their fortunes to philanthropy.
Mr Buffett's statement also addressed recent criticism after a ProPublica investigation found that he and other wealthy people paid low taxes relative to their fortunes.
He said his donations have resulted in only about 40 cents of tax savings per $1,000 given.