Banks will be forced to hold a bigger capital buffer against complex assets and high-risk trades under new rules proposed yesterday by the world's most powerful banking regulator.

The Basle Committee for Banking Supervision said that banks should ensure that they have easy access to cash to avoid a repeat of the Northern Rock debacle. Nout Wellink, the committee's chairman, said: “Supervisors cannot predict the next crisis but they can carry forward the lessons from recent events to promote a more resilient banking system that can weather shocks.”

Analysts said that much of the report was a case of shutting the stable door after the horse had bolted. Krishnan Ramadurai, managing director in fixed income at Fitch Ratings, said that most of the high-risk assets had already disappeared from the market. “But it doesn't hurt to remind people, because memories are short and similar situations will no doubt arise again,” he said.

Financial regulators from around the world contributed to the committee's report, which is one of several recently released on the cause and impact of the credit crunch. The Financial Stability Forum has called for greater supervision of bank activities, while the Institute of International Finance admitted that banks had made a series of blunders in the lead-up to the liquidity squeeze. The Financial Services Authority is due to release a report on liquidity next month, before a full consultation paper in the summer.

The Basle committee said that it would revise its capital adequacy framework to force banks to hold larger capital cushions if they dealt in products such as collateralised debt obligations made of asset-backed securities. Other securities, particularly those backed by mortgages sold to poor Americans, caused the greatest losses in the credit crunch.

Banks that hold complex securities in their own trading books will have to put aside more risk capital under the committee's new rules. The committee said that it would put out a report in July on how banks and regulators could better manage their liquidity risks. Guidance will be published next year on the best ways for banks to disclose their exposures to complex securities.

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