LONDON (Reuters) - Britain's top fraud prosecutor said on Tuesday it had charged former UBS trader Tom Hayes with eight counts of conspiracy to defraud in connection with an investigation into benchmark interest rate manipulation.

Hayes, 33, who was arrested by police and the Serious Fraud Office last December alongside two other traders, has been painted by authorities as a key figure in an inquiry stretching from the U.S. to Japan. He was charged by U.S. prosecutors last year.

Authorities are jostling to nail those they say conspired for years to manipulate Libor (the London interbank offered rate) - a crucial benchmark affecting trillions of dollars of mortgages and other loans worldwide.

(Reporting by Kirstin Ridley, Editing by Sinead Cruise)