An Anglo-French summit on Thursday will put renewed pressure on banks to agree to "full and immediate disclosure" of the scale of their bad debts, reflecting heightened political concerns about instability in financial markets.

Gordon Brown, the British prime minister, and Nicolas Sarkozy, France's president, will make the call for greater bank transparency a central element of their talks in the UK this week. European finance ministers said in January that slow and inconsistent disclosure of bad debts by banks exposed to the subprime market was damaging confidence.