The drive to relieve the debts of the world's poorest countries, perhaps the most high-profile global campaign of modern times, reached the end of an era this year with the winding up of the organisations dedicated to campaigning for it.

The debt relief scheme is now into the critical implementation phase, testing long-standing questions about whether it will have a lasting impact. And, as well as monitoring the initiative, development campaigners are casting around for something with the same direct emotional appeal to push the cause of poorest countries.

Drop the Debt, the successor campaign to Jubilee 2000, wound itself up after the Group of Eight summit in Genoa in July when world leaders met amid the teargas to agree that the scheme was beginning to work and that there was no immediate need to change it.

The Drop the Debt campaign had concentrated on trying to increase the amount of relief on offer from the International Monetary Fund and the World Bank to the 40 or so countries eligible up to 100 per cent of debts. The G8 did not comply. Adrian Lovett, the then director of Drop the Debt - now director of campaigns at Oxfam - said: "The G8 leaders had a golden opportunity to finish the work they started on debt two years ago. This is the sort of thing that gives the G8 such a bad name."

Drop the Debt's argument was that relief on offer - which reduces the debt stock of the countries to 150 per cent of their exports or 250 per cent of fiscal revenue - was inadequate to gain lasting exit from heavy indebtedness and low growth.

In the end, there was no more than lukewarm support from any of the IMF and World Bank's large shareholder countries for extending the scheme. A feeling that it could reduce the financial institutions' capacity to lend, and that it would be unfair to countries like Bangladesh which are also very poor but have a lower debt stock prevented any member of the G8 picking up the idea and running with it.

Although the immediate pressure for more debt relief is likely to abate, the scheme is in many ways entering a critical phase. With at least 24 countries already having qualified for the first stage of interim relief, and now planning for full relief, the ability of the initiative to pro vide a permanent exit from indebtedness will be tested.

One particular difficulty is that the debt relief currently promised to qualifying countries may not be enough even to get them to the short-term targets for debt sustainability. A report prepared for the executive boards of the World Bank and International Monetary Fund has warned that for some countries dependent on commodity exports, movements in commodity prices meant the debt/export ratio targets might not be met.

The report said that debt reduction targets were under threat in countries like Niger, which has been hit by falling uranium prices, and Uganda, which has suffered as coffee and cotton prices have slid on world markets. Since then, the downward pressure on commodity prices as a result of the September 11 attacks and the global downturn has increased the probability that further relief will be needed. Despite pressure from the US not to offer a blank cheque for debt relief, the IMF and World Bank have admitted they will have to rethink the amount of relief on offer, if the deterioration persists.

One critical aspect remains the amount of new aid which will flow to the heavily indebted poor countries (HIPC) and other states. The bank has estimated that aid will need to double to more than $100bn a year if the United Nations 2015 development targets are to be met.

Gordon Brown, the UK chancellor, stepped up the pressure on fellow governments - and his own - by calling for an extra $50bn of aid a year just before the recent meetings of the World Bank and IMF ministerial committees in Ottawa. Kofi Annan, the UN secretary-general, attended the meetings to make a similar plea for more money ahead of a UN-convened meeting on financing for development in Mexico next year.

Ideas like a global "Tobin tax" on currency transactions, or a global carbon tax - which was floated by a blue-ribbon commission headed by former Mexican president Ernesto Zedillo earlier this year - now look less like wishful thinking.

Much will depend on the US. Paul O'Neill, the US treasury secretary, seemed distinctly cool about Mr Brown's call for more aid during the Ottawa meetings, referring instead to the large amounts of money that have been spent in the name of development before with no discernible achievement. The US, as one of the lowest givers of foreign aid as a proportion of its national income, and with a dominant role in the World Bank and the IMF, will be important to achieving a substantial shift in aid giving.

Another area on which development campaigners have increasingly focused is trade. Although many were unhappy with the recent agreement on a new round of trade talks in Doha, they did at least see it as an opportunity to push the idea of poor country access to rich country markets.

Bono, the rock star with the group U2 who helped to raise the profile of the debt relief campaign, says that the new realisation of interdependence between rich and poor countries is an opportunity for campaigners. "The new trinity is debt, aid and trade," he says. "NGOs have broadened their agenda and now see a window of opportunity to move forward on all three."