European Union antitrust regulators charged UBS, UniCredit and Nomura with a fine of £319m for their connections with a European government bond trading cartel.
The sizable fines are the most recent punishment of the financial industry for its alleged involvement in foreign exchange cartels, Euribor and Libor benchmark cartels, and bonds cartels.
The European Commission has said that the European government bond cartel ran for four years between 2007 and 2011, with traders from the banks informing each other on their prices.
The Commission has also said that prices were shown to their customers or to the wider market through chat rooms on Bloomberg terminals.
European Competition Commissioner Margrethe Vestager said in a statement: “A well-functioning European government bonds market is paramount both for the eurozone member states issuing these bonds to generate liquidity and the investors buying and trading them.”
All three banks in statements said that they were considering or planning to appeal.
The European Commission said Bank of America, RBS (now known as NatWest), Natixis and WestLB (now known as Portigon) also played a part in the cartel.
NatWest avoided a €260m fine because it alerted the cartel to the EU competition watchdog.
Bank of America and Natixis were not fined because their infringement falls outside the limitation period for imposition of fines while Portigon was exempt because it generated zero net turnover in the last business year.