Royal Bank of Scotland is among six major banks fined a total £3.8bn for trying to manipulate foreign exchange rates.

RBS pleaded guilty today - along with JPMorgan, Citigroup, Barclays - to trying to manipulate foreign exchange rates, according to US offficials. RBS was fined £430m ($669m).

In total, authorities in the United States and Europe have fined seven banks over £6.4bn ($10bn) for failing to stop their forex traders from sharing confidential information about client orders and coordinating trades to boost their own profits.

Traders at Citigroup, JP Morgan, Barclays and Royal Bank of Scotland, who described themselves as "The Cartel", used an invitation-only electronic chatroom and coded language to manipulate the price of U.S. dollars and euros between December 2007 and January 2013, according to U.S authorities.

The four banks pleaded guilty to conspiring to manipulate the foreign exchange market.

Barclays faced the biggest fine with a penalty of £1.5 billion ($2.4bn) because it did not join in an earlier November settlement with British and some U.S. authorities due to complications with its regulator in New York.

"Put simply, Barclays employees helped rig the foreign exchange market. They engaged in a brazen 'heads I win, tails you lose' scheme to rip off their clients," Benjamin Lawsky said in a statement. "While today's action concerns misconduct in spot trading, there is additional work ahead."

Barclays had set aside £2bn ($3.2bn) to cover any forex related settlement. Shares in the bank rose more than two percent.

Swiss bank UBS, which avoided a guilty plea over the forex debacle, pleaded guilty instead to one count of wire fraud and will pay a (£130) $203 million fine for its role in rigging Libor after its involvement in the forex scandal breached an earlier DOJ agreement.

The U.S. central bank fined six banks for unsafe and unsound practices in the foreign exchange markets, including a £132m ($205m) fine for Bank of America, which, like UBS, avoided a guilty plea.