Employees of some of the world's largest financial institutions conspired with a former bank trader to rig benchmark interest rates, British prosecutors alleged yesterday, the Wall Street Journal reported today. The U.K.'s Serious Fraud Office this week charged former UBS AG and Citigroup Inc. trader Tom Hayes with eight counts of "conspiring to defraud" in an alleged attempt to manipulate the London interbank offered rate, or Libor. Hayes, who was charged with similar offenses by the U.S. last December, hasn't entered a plea to either country's charges. The charges read in court yesterday accuse Hayes of allegedly conspiring with employees of eight banks and interdealer brokerage firms, as well as with former colleagues at UBS and Citigroup. The banks include New York-based J.P. Morgan Chase & Co., Germany's Deutsche Bank AG, British banks HSBC Holdings PLC and Royal Bank of Scotland Group PLC and Dutch lender Rabobank Groep NV.