Invitations have been sent out to senior bankers and regulators to form a new group to tackle the problems of valuing securities in illiquid markets – an issue central to the credit crunch and banks’ complaints about the write-downs they have been forced to report.

Financial institutions have taken more than $300bn of write-downs, many of them directly hitting profits, as the market seizures led prices to plummet. In many cases, values are expected to be at least partly written back up as markets recover.