Members of Congress and international campaigners are turning the spotlight on what they call the immoral behaviour of "vulture funds" ahead of next month's Group of Eight summit of industrialised nations in Germany, warning that the funds threaten to undermine debt relief for Africa's poorest.

The funds were "feeding upon financially distressed nations" and court cases against developing countries were "morally reprehensible and exploitative", Donald Payne, Democratic chairman of the House subcommittee on Africa and Global Health, told a hearing this week.