Prosecutors in the UK plan to file criminal fraud charges against a former trader at UBS and Citigroup who allegedly was at the center of efforts by several banks to manipulate interest rates, people familiar with the plans said.

Tom Hayes, a 33-year-old British citizen living near London, could face charges from the UK's Serious Fraud Office as soon as Tuesday. It would be the first move by UK authorities to seek criminal penalties against anyone allegedly involved in rigging the London interbank offered rate, or Libor, a benchmark used to set interest rates on trillions of dollars of financial contracts, ranging from mortgages to derivatives.