Libor borrowing rates must be replaced soon as possible as it is “unsustainable” to continue to use them, the top US regulator overseeing a global effort to reform the benchmarks for global financial markets has urged.

Gary Gensler, head of the Commodity Futures Trading Commission, told the Financial Times that Libor replacements were needed “to restore market integrity and promote financial stability”.

Mr Gensler has led the global rate-rigging probe that has extracted more than $2.6bn in fines from three banks and investigated nearly a dozen other groups. He has been openly sceptical of interbank lending rates since last autumn, but his remarks are the strongest signal yet that regulators will scrap the London Interbank Offered Rate in its current form and find an alternative benchmark for the more than $350tn contracts that reference it.