Barclays has been fined £26 million ($43.8 million) for control failings over its setting of gold prices, which occurred just a day after the British bank was fined $450 million for rigging Libor interest rates.
It is the first bank to be fined over attempted gold market manipulation, although a source said the Barclays fine was a one-off case and not part of a wider investigation into gold market price rigging.
It marks another blow to Barclays' attempts to put past problems behind it.
The Financial Conduct Authority said there were failings at Barclays from 2004 until 2013, but the key event occurred on June 28, 2012.
It banned former Barclays trader Daniel James Plunkett for exploiting weaknesses in the British bank's systems.
"A firm's lack of controls and a trader's disregard for a customer's interests have allowed the financial services industry's reputation to be sullied again," said Tracey McDermott, the FCA's director of enforcement and financial crime.
"Plunkett's actions came the day after the publication of our Libor and Euribor action against Barclays. The investigation and outcomes in that case meant that the firm, and Plunkett, were clearly on notice of the potential for conflicts of interests around benchmarks," she said.