The US on Wednesday called for the World Bank to enlarge its capacity to lend during financial crises, a role the bank has often resisted.

Larry Summers, US treasury secretary, also urged in a speech in Washington that the International Monetary Fund and World Bank stop so-called defensive lending - making of new loans to ensure past lending is repaid.

He said this was important to ensure that poor countries now benefiting from debt relief did not fall back into debt, but his comments have relevance for countries such as Russia, where the IMF has in the past been criticised for lending only to protect previous loans.

Mr Summers, speaking ahead of the annual IMF - World Bank meetings, said the World Bank and regional development banks needed to expand their capacity to provide emergency financing in times of crisis. These would help cushion fiscal squeezes that were often necessary in economic stabilisation, thereby protecting the poor as well as providing finance for bank restructuring.

The banks should also look at expanding the pilot programmes they have introduced to make more effective use of guarantees, he said.

He said he supported the effort to bring 20 countries this year into the debt relief initiative intended to benefit the most heavily-indebted poor countries. He called on the World Bank to move quickly to put in place new lending instruments to provide low-cost aid to the poorest countries, thereby making explicit US backing for a proposed Poverty Reduction Support Credit (PRSC).

He said it was most important that countries that receive debt reduction do not fall into similar troubles in future.

It also meant the institutions should be more selective about providing non-concessional loans to countries that have been recipients of debt relief. For this reason, the World Bank's capacity to make grants through its International Development Agency subsidiary should be substantially increased.

Gordon Brown, the UK chancellor, who chairs the IMF's influential International Monetary and Financial Committee, said on Wednesday that the IMF should broaden its surveillance of member countries.

He echoed comments by Horst Köhler, the IMF's managing director, that prevention of financial crises was as important as their resolution.

Mr Brown said the IMF's regular Article IV reports on countries should be widened to include compliance with international standards and codes of policy-making as well as macroeconomic policy. "It must become transparent so that the public and the markets get the information they need and have confidence in the process which produces it," he said.

Mr Brown also said the IMF needed to set out a "clear set of presumptions" for the involvement of private sector investors in solving financial crises. Attempts to involve private investors in rescheduling debt in crisis-ridden countries have often been a source of disagreement within the IMF's governing board, with several European countries arguing for fixed rules to apply in all cases, and the US preferring a flexible case-by-case basis.