The U.S. Department of Justice and the Securities and Exchange Commission are investigating whether the group's relationships with third parties, including the Qatari investors, violated the U.S. Foreign Corrupt Practices act. The Federal Reserve has asked to be kept informed.
"It is not possible to estimate the full impact on the Group if the final conclusion of these matters is adverse," Barclays said in its third-quarter earnings statement.
Barclays reported that net income fell 26 percent to 2.8 billion pounds for the 9-month period ending in September. The bank attributed the decline to its "Transform," program, which aims to reduce risk after the financial crisis and change the culture of the bank.
"The FX review is something of a concern and adds to the ongoing investigations," said Richard Hunter of Hargreaves Lansdown, a London-based stockbroker and asset manager. "In addition, the costs of transforming the bank have impacted negatively on both operating expenses and therefore the cost income ratio."
Barclays has been troubled by scandal in recent years, having been fined by regulators in the U.S. and Britain for manipulating the London interbank offered rate, or LIBOR, the benchmark for trillions of dollars in loans including some home mortgages
The brash American CEO, Bob Diamond, was forced to resign in the scandal. Other troubles included the mis-selling of insurance and interest rate products to consumers and small businesses.