Money markets in the US and Europe are signalling renewed fears about the financial strength of banks, with key confidence barometers almost returning to the levels that preceded the collapse of Bear Stearns.

The concerns are being highlighted by the difference between overnight lending rates set by central banks and three-month Libor, the rate at which banks lend to each other. This spread, known as the overnight index swap rate, has been rising in the US and remains elevated in Europe, indicating that banks are reluctant to lend to each other.