Fines of just £104 million have been dished out to bankers from HSBC Holdings PLC (LSE:HSBA), Citigroup Inc (NYSE:C), Morgan Stanley (NYSE:MS) and Royal Bank of Canada (TSX:RY) for rigging UK government bond sales.
The bankers unlawfully shared what would normally be competitively sensitive information about aspects of the pricing of gilts between 2009-2013, using Bloomberg's one-to-one chat messaging platform.
The UK Competition & Markets Authority said the banks, including Deutsche Bank, which was given immunity for handing itself in, avoided much higher fines by taking "unusually extensive steps" to ensure the behaviour would not happen again.
Gilts, which the UK government sells to raise money to finance public spending, are likely to have been issued with artificially lower prices and higher interest rates, also known as yields, as collusion was made during the sale of gilts by the UK Debt Management Office via auctions on behalf of HM Treasury.
Some of the collusion involved subsequent trading of gilts and gilt asset swaps, and some during the 'buyback' process of selling gilts back to the Bank of England.
Juliette Enser, executive director of competition enforcement at the CMA, said the cases were settled with the five banks following a "constructive engagement between" the banks and the authority, and the fines would have been substantially higher had the banks not already taken to make sure that this doesn't happen again
"The financial services sector is an integral part of the UK economy, contributing billions every year, and it's essential that it functions effectively."
She said the fines "reflect the CMA's commitment to dealing with competition law breaches and deterring anti-competitive conduct".
The last exchanges between the banks occurred in 2010 for HSBC, 2012 for Morgan Stanley, and 2013 for Citi, Deutsche Bank and RBC.
HSBC was fined £23.4 million after a 10% reduction for settling with the CMA after an initial statement of objections was made to the FTSE 100-listed bank
Canadian lender RBC was fined the most, £34.2 million, also after a 10% reduction.
US banks Morgan Stanley and Citi were fined £29.7 million and £17.2 million respectively but while the former got a 10% reduction Citi was given a 35% leniency discount and a 20% reduction for settling in advance of the CMA issuing its objections.
Citi's fine would have been £38.2 million if it did not receive discounts or reductions, while RBC's would be £38 million, Morgan Stanley £33 million and HSBC £26 million.