Shares of British banking giant Standard Chartered fell more than 23% on the London Stock Exchange Tuesday, one day after New York regulators accused the banking group of helping Iran avoid sanctions by concealing $250 billion in transactions over nearly 10 years. On Monday, the New York State Department of Financial Services accused the London-based bank of conspiring to hide 60,000 transactions with Iranian clients, including the Central Bank of Iran, from 2001 to 2010. Liberum Capital analyst Cormac Leech said Tuesday that Standard Chartered could face up to $5.5 billion in costs, including fines, lost revenue and damage to the bank's staid reputation. Leech added that it's unclear whether senior managers at Standard Chartered will resign over the accusations. Federal regulators and the U.S. Department of Justice could bring charges against Standard Chartered for violations of bank security laws and anti-money laundering regulations, among other things, according to John Alan James, an expert on corporate governance at Pace University in New York.