Aug. 7 (Bloomberg) — Standard Chartered Plc fell the most in almost 24 years as an analyst estimated it may face costs of $5.5 billion after being accused of violating U.S. money laundering laws over to its dealings with Iranian banks.

The shares fell 23 percent to 1,132 pence by 10:42 a.m. in London trading, their biggest decline since 1988, the earliest date for which data are available.

Standard Chartered may lose its license to operate in New York after the state's Department of Financial Services found the bank conducted $250 billion of deals with Iranian banks over seven years and earned hundreds of millions of dollars in fees for handling transactions for institutions subject to U.S. economic sanctions. The London-based lender today denied the allegations, saying it "strongly rejects the position and portrayal of facts" made by the regulator.