The world’s leading banks have stepped up pressure to relax controversial accounting rules with a new plan aimed at breaking the “downward spiral” of huge writedowns, emergency fundraisings and fire-sales of assets.

The proposals on “fair value” accounting by the Institute of International Finance, an alliance of 300-plus companies chaired by Josef Ackermann, Deutsche Bank’s chairman, would enable financial companies to cushion the blow of financial crises by valuing illiquid assets using historical, rather than market, prices.