Britain's markets watchdog has fined Barclays STG72 million ($A150.30 million) for failing to minimise the risk that it might be used to aid financial crime.
The Financial Conduct Authority (FCA) said the failings relate to a STG1.88 billion pound transaction that Barclays arranged and executed in 2011 and 2012 for a number of ultra-high net worth clients.
"The clients involved were politically exposed persons and should therefore have been subject to enhanced levels of due diligence and monitoring by Barclays," the FCA said in a statement.
"Barclays did not follow its standard procedures, preferring instead to take on the clients as quickly as possible and thereby generated STG52.3 million in revenue."
The fine is the largest levied by UK regulators for financial crime failings.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
The FCA said the bank went to "unacceptable lengths to accommodate the clients", failing to ask for key information as it "did not wish to inconvenience" them.
Barclays agreed keep details of the transaction under wraps even within the firm, agreeing to a clause that would see the clients paid STG37.7 million if they failed to comply with the confidentiality agreement.
The bank did not keep records of its due diligence relating to the transaction on any of its systems, instead keeping only hard copies, with few people aware of their existence or location, according to the FCA.
