The biggest threat to central banks' independence comes from governments pushing them to finance large fiscal deficits, Bank of England chief economist Huw Pill said, Bloomberg reported Thursday.

Pill, who sits on the BOE's Monetary Policy Committee, said how central banks manage such risks is the "defining challenge they currently face," Bloomberg reported, citing an interview with Moneyfacts' INTEREST journal.

Slow growth and supply shocks have driven up deficits and public debt globally, and financing those deficits through central banks could call their independence into question, Pill said, according to the report.