To set Libor, which underpins hundreds of trillions of dollars in assets around the world, banks submit market data, or — when these numbers are lacking — use their own estimates to inform submissions. That process has prompted questions about the benchmark’s accuracy, and helped fuel a years-long push to replace it.

“Over half of the 35 published Libor rates across all currencies contained no transaction-based submissions at all” during the week of March 16, Bailey said. “At the same time, Libor rates, and therefore costs for borrowers, spiked upwards based on firms’ expert judgment.”

Transaction-based submissions in three-month sterling Libor dropped to zero during the week of March 16, according to Bailey.

Regulators began phasing out the Libor benchmark after European and U.S. banks were found to have manipulated rates to benefit their own portfolios, with lenders and companies supposed to make the leap over the next 18 months. Yet those efforts have stumbled as market participants shifted attention away from the transition and toward surviving the crisis.

“Despite the array of challenges we’re facing as a result of the coronavirus, transitioning away from Libor continues to be of paramount importance,” New York Fed President John Williams said, during the online Bloomberg event.

Bailey warned of a crackdown if banks don’t show they are moving away from Libor.

“We would not expect to see any further sterling Libor linked lending after the end of March 2021,” he said. “Regulated firms in the U.K. should expect their supervisors to monitor and discuss their progress with these important milestones.”