“JPMorgan Chase, which emerged from the financial crisis as the nation’s biggest bank, disclosed on Thursday that it had lost more than $2 billion in trading, a surprising stumble that promises to escalate the debate over whether regulations need to rein in trading by banks.”

“Jamie Dimon, the chief executive of JPMorgan, blamed “errors, sloppiness and bad judgment” for the loss, which stemmed from a hedging strategy that backfired.”

“The trading in that hedge roiled markets a month ago, when rumors started circulating of a JPMorgan trader in London whose bets were so big that he was nicknamed ‘the London Whale’ and ‘Voldemort,’ after the Harry Potter villain.”

…

“ ‘JPMorgan Chase C.E.O. Jamie Dimon has been a relentless critic of financial reform,’ said Dennis Kelleher, president of Better Markets, which supports tougher regulation of banks. The surprise loss, he said, ‘proves him wrong.’ ”

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Read full New York Times DealBook article here.