Everyone at last week's G20 meeting was pretty much agreed — detoxing the banks of their poisonous assets was a necessary condition for global economic recovery. Curious then that so little was said about the issue in the official communiqué.

The world leaders pointed to what had already been done in terms of recapitalising banks and dealing with their impaired assets. And they underlined their commitment to do whatever was required in the future to restore the normal flow of credit. But that was it.

Experience of previous banking crises suggests that what is required is a comprehensive and systematic approach to bank balance sheets. Yet the approach we have at the moment remains ad hoc and piecemeal.

In Britain great strides have been made both in recapitalising the banks and ring-fencing their toxic assets. The taxpayer has put £37 billion directly into RBS and Lloyds; Barclays has raised £7.3 billion from investors and is expected to bring in another £3 billion from the sale of iShares; and HSBC has just wrapped up a very successful £12.5 billion rights issue. In terms of toxic debt, RBS and Lloyds have taken out insurance with the Government covering potential losses on almost £600 billion of assets.

Even so, some analysts believe more will be needed. Yet Britain is much further down the road than many other countries. And meanwhile, the scale of the problem just keeps mounting.

Only in January the International Monetary Fund doubled its forecast of total losses on US credit assets to $2,200 billion (£1,490 billion). As a result, it estimated that US and European banks would need to raise $500 billion to prevent their balance sheets from deteriorating further.

Now I hear that the IMF's economists are preparing to increase that figure to $3,100 billion, with a further $900 billion for assets originated in Europe and Asia.

This escalation reflects the spreading of the downturn from US property-related securities to the real economy around the world. Banks exposed to the crisis in central and eastern Europe look particularly vulnerable.

In a joint report by Morgan Stanley and the consultants Oliver Wyman, the authors argue that continental European governments need to come up with a more comprehensive approach to bolstering their banks, many of which have perilously thin capital cushions.

Meanwhile in the US, Mike Mayo, a veteran banking analyst now at Calyon Securities, warns that the worst is yet to come. He says that government action on impaired assets could trigger the need for further large capital increases for US banks.

The problem is that ploughing more taxpayers' money into their undeserving banks is politically toxic. What politicians need is the cover provided by concerted global action. And they need it before the next G20 summit. Now that Mr Sarkozy and Ms Merkel have their crackdown on tax havens, perhaps they can show some leadership on more urgent problems.

Times Recommends

• Lies and cover-up at MG Rover exposed by report
• High oil prices push manufacturing costs up
• Primark founder steps down as chief executive