Bank stocks were boosted on Thursday by an accounting rule change that is expected to allow managers to repair balance sheets by recalculating the value of some of their most troubled assets.

The Financial Accounting Standards Board voted on Thursday morning to allow banks more freedom to use their own valuation models, rather than current market prices, for assets where markets have become illiquid. A second rule change means banks will only have to recognise a part of any impairment in their profits.