Several other global banks are also under investigation for suspected manipulation of key interest rates, it has emerged.
Yesterday (27 June), Barclays was hit with penalties totalling £290 million ($450 million) from regulators on both sides of the Atlantic after investigations established it had committed serious misconduct in this area between 2005 and 2009.
Included in these fines was a £59.5 million fine from the Financial Services Authority (FSA) - and Tracey McDermott, acting director of enforcement and financial crime at the body, has revealed the financier is unlikely to be the only firm penalized.
Speaking to the BBC, Ms McDermott noted: "We have a number of investigations that are ongoing."
"Obviously we need to look at each case on its own particular facts but the initial indications are that Barclays was not the only firm that was involved in this," she added.
It is thought that household names in the banking industry such as HSBC, Citigroup and the Royal Bank of Scotland are among those companies facing scrutiny.
By Claire Archer