New York's top financial regulator accused a Standard Chartered unit of running a "rogue institution" that "schemed" with Iran's government to hide more than $250bn in illegal transactions for nearly a decade.

The allegations were made in a 27-page order filed Monday by Benjamin Lawsky, superintendent of the New York State Department of Financial Services. Lawsky said the agency's ongoing investigation of the UK bank also "has uncovered evidence with respect to what are apparently similar schemes" by a Standard Chartered subsidiary in New York "to conduct business with other US sanctioned countries, such as Libya, Burma and Sudan."