LONDON — Shares in major British banks fell today in the first day of trading after JPMorgan Chase revealed a loss of $2 billion in six weeks in trading on derivatives by its London operation.

Barclays, which has a large investment banking arm, was the biggest loser in London trading this morning, down 2.9 percent at 202.7 pence in midmorning trading.

Royal Bank of Scotland fell 2.2 percent, while Lloyds Banking Group was down 1.8 percent and HSBC dipped 1.3 percent.

“Based on the limited information available, it’s attributed to egregious error within JP Morgan, so there is no reason to read across that specific loss to any other bank,” said Ian Gordon, analyst at Investec Securities.

JPMorgan Chase, the largest bank in the United States, said it lost $2 billion in the past six weeks in a trading portfolio designed to hedge against risks the company takes with its own money.