British prosecutors filed criminal fraud charges on Tuesday against Tom Hayes, a former UBS and Citigroup trader accused of playing an integral role in the ma­nipu­la­tion of the global interest rate known as Libor.

Britain’s actions come seven months after the U.S. Justice Department filed a similar case against Hayes and a former colleague at UBS as part of a $1.5 billion settlement with the Swiss banking giant. The two traders are the only individuals to date to face criminal charges in the banking scandal.

Britain’s Serious Fraud Office is charging Hayes, 33, with eight counts of fraud for allegedly conspiring to rig Libor, the London interbank offered rate. He was one of three people arrested and questioned in London in the scandal at the end of the year, according to British authorities. Hayes, who could not be reached for comment, was released on bail. His attorneys at Fulcrum Chambers in London declined to comment.

Allegations against Hayes first came to light in December, when UBS became the second international bank — Barclays being the first — to own up to its role in the rate-fixing.

UBS is one of 16 institutions, including JPMorgan Chase, Bank of America, Citigroup and HSBC, that submit data to set the daily Libor rate. The interest rate is supposed to reflect the rate at which banks lend to one another and is used as a benchmark for other interest rates around the world.

Prosecutors say a cadre of traders and senior managers at UBS colluded with at least four other banks and pressured brokers to spread false data to manipulate multiple global interest rates. The changes could have caused banks to appear healthier than they really were during the financial crisis of 2007 and 2008 by suggesting that they were trading with low interest rates. But the actions also could have allowed banks to rig financial trades to create profits.

In December, the Japanese subsidiary of UBS pleaded guilty to criminal charges of felony wire fraud filed by U.S. authorities. The agency said it did not prosecute the parent company because of the bank’s cooperation with the investigation.

The U.S. Commodity Futures Trading Commission was the first to uncover evidence that something was amiss with the rates in 2005. The agency discovered that Barclays senior management and numerous traders in London, New York and Tokyo were making false reports to improve the bank’s trading position, dating back to 2005.

The Justice Department has used information provided by Barclays for continuing criminal investigations into other banks and bank employees. But U.S. prosecutors may hit a wall in their case against Hayes because of the charges the trader faces in London.

British double-jeopardy laws prevent anyone charged in the United Kingdom from being extradited to face similar charges in another country, according to James Gurule, a law professor at the University of Notre Dame. Officials at the Justice Department declined to comment on the issue.

Critics of the Libor investigation say prosecutors have not gone far enough to clamp down on banking misconduct, with few executives indicted so far despite the broad scope of evidence uncovered.

“You would think by now there would be more than criminal charges . . . the scandal certainly wasn’t committed by a single person,” said Gurule, a former undersecretary of enforcement for the Treasury Department. “It could be this is a starting point, and [Hayes] may provide information to implicate others.”

In recent months, U.S. and British authorities have launched probes into the ma­nipu­la­tion of another key market benchmark, ISDAfix. The benchmark for the $379 trillion swaps market is based on submissions made to London-based ICAP by 13 banks, including JPMorgan Chase and Goldman Sachs.

Britain’s Financial Conduct Authority and the CFTC are investigating whether traders at the banks colluded with ICAP brokers to manipulate the rate, according to British authorities. Officials at CFTC declined to comment, as did the banks involved in submitting the rate. ICAP acknowledged that the investigation was ongoing but would not provide any further details.