The U.S. Justice Department is preparing to file charges this fall against traders from several banks in the global probe of interest-rate rigging, but prosecutors in Britain haven’t even decided whether they have a case.

The United Kingdom’s Serious Fraud Office (SFO) opened a criminal investigation this month after Barclays was fined a record $450 million by British and U.S. authorities. Politicians including Chancellor of the Exchequer George Osborne and Ed Miliband, leader of the opposition Labor Party, called for a criminal probe, and the agency was told it would be given a budget to take on the case.

The SFO had declined to get involved in the investigation for more than a year, despite briefings with the U.K. Financial Services Authority and a compilation of findings from U.S. enforcement agents. The U.S. evidence was provided late last year, according to a person familiar with the case who wasn’t authorized to discuss it.

“It’s partly the difference in culture,” said Andrew Haynes, a law professor at the University of Wolverhampton in England. “In America, economic crime is something that’s regarded as desperately serious. In this country it is regarded as a problem, but there’s sometimes a slothful response.”

The United Kingdom joins the United States in criminally investigating how derivatives traders and rate submitters colluded to rig the London Interbank Offered Rate, or Libor, and other interest rates. At least a dozen banks are being probed by regulators worldwide. Royal Bank of Scotland Group, UBS, Deutsche Bank and Credit Suisse Group are among banks awaiting their fate as regulators from Tokyo to London to New York investigate.

“Now the priority is to come to an assessment whether the available offenses are there for us to prosecute in a criminal court,” SFO spokesman David Jones said. If “the answer to that is yes we can, then we start going hell for leather and putting together a formal investigation team,” he said.

Barclays on Friday apologized for its role in the Libor scandal as it posted a first-half profit that beat analyst estimates and disclosed that it was the target of more Libor-linked lawsuits.

Barclays employees tried to manipulate the Euro Interbank Offered Rate, or Euribor, and Libor for profit, while managers instructed rate-setters to make artificially low submissions to avoid the perception the lender was under stress amid turmoil in credit markets in 2007 and 2008, according to the settlement.

As part of the U.S. and British settlements, Barclays admitted rigging rates as early as 2005. Chief executive officer Robert Diamond and chief operating officer Jerry Del Missier resigned over the scandal.

The U.S. charges against individuals, which would probably be filed by October, center on alleged rate-fixing activity that goes beyond the conduct described in last month’s settlement between Barclays and regulators, according to the person familiar with the case.

The Justice Department probe of criminal activity related to Libor is moving on a parallel course with civil probes of the banks by the Commodity Futures Trading Commission, the Securities and Exchange Commission and British regulators, including the SFO.

— Bloomberg News