The chairmen of two US congressional committees are warning that the project evaluation standards of the Asian Development Bank are set to be watered down to unacceptable levels.

In a joint letter seen by the Financial Times, Patrick Leahy and Barney Frank, the respective chairmen of the Senate judiciary and House financial services committees, urge Hank Paulson, the US Treasury secretary, to demand that the ADB stick to tougher environmental and social criteria for approving project financing than what is currently foreseen in its planned policy overhaul.