The British bank Standard Chartered has rejected a US regulator's claim that it hid $250bn in transactions with Iranian banks in violation of US sanctions.

The denial came on Tuesday, a day after New York's Department of Financial Services (DFS) threatened to revoke the bank's licence and impose fines, as the regulator branded the London-based lender as a "rogue bank".

"The group strongly rejects the position or the portrayal of facts as set out in the order issued by the DFS," group company secretary Annemarie Durbin said in a statement.

"The group does not believe the order issued by the DFS presents a full and accurate picture of the facts."

Shares of Standard Chartered fell by as much as a quarter in trading in London and 7.5 per cent on the Hong Kong stock exchange, as there are fears the bank could lose its operating licence in the US.