As the 2015 deadline approaches for achieving the "Millennium Development Goals" – the global benchmarks for tackling poverty – questions are growing louder about how far we’ve come, and what we do next. David Cameron is to co-chair a UN High-Level Panel on this "post-2015" agenda. At conference tables, across the blogosphere and in an avalanche of reports, donors and development experts are starting to haggle over the future of aid and development.  

Cameron has set out his stall already, describing his vision of a "golden thread" of development through tackling corruption; securing rights; and shifting focus from aid to economic growth, led by business and private enterprise. Cameron’s co-chairs, Presidents Susilo Yudhoyono of Indonesia and Ellen Johnson Sirleaf of Liberia, also want to look beyond aid to unlock wealth through “economic growth, trade, tackling corruption, effective government and open societies”.

There’s no denying that a re-think is needed. The world has profoundly changed since the MDGs were conceived in the 1990s. With persistent crises in wealthy economies, global aid levels fell last year for the first time since 1997. The UK government is still rightly committed to reaching the UN agreed target of spending 0.7 per cent of national income on aid, and though it will remain vital for many years to come, it’s high time to also look for new resources to fight poverty.

At the same time, we’ve witnessed a seismic shift in the geography of economic growth and potential. It’s now clear that Asian and African economies will continue to grow far faster than in Europe and North America. The boom is far from universal, but nor is it confined to the new "big beasts" of the global economy. In the last decade some sub-Saharan African countries have experienced growth rates higher than Brazil and China – but with health, education and incomes lagging far behind in many places. 

Cameron and his co-chairs rightly acclaim the world-changing potential of this economic transformation – but the poorest citizens are yet to see its impact.  Certainly efforts to tackle poverty must draw more from developing countries’ own growth and resources, far more reliable than volatile aid flows. But the global development challenge is now neither simply to increase aid, nor just to help developing countries to attract private investment and promote growth. It is to convert the rewards of investment and growth into jobs, incomes, health and education for citizens. 

This can only happen if developing countries are able to raise their own revenue fairly, and spend it equitably. Financing the fight against poverty requires companies, investors and wealthy individuals to pay their taxes due. Yet the OECD has estimated that developing countries lose more to tax havens than they receive in aid. ActionAid estimates that just one multinational company we investigated, the FTSE100 drinks giant SABMiller, has avoided £20m a year in taxes across Africa and Asia – enough to put an extra 250,000 children in school – helped by shifting profits through a network of companies in Switzerland, Mauritius and the Netherlands. 

Most developed countries collect between 30 and 50 per cent of their GDP in tax revenue. In sub-Saharan Africa the average is just 17 per cent. How can we help bridge the gap? Aid can help. Assistance to revenue authorities in developing countries to combat tax dodging is some of the most cost-effective aid imaginable. The Rwanda Revenue Authority was set up in 1998 with the help of a £20m grant from the UK – the same amount it now collects in revenues every four weeks. Equally vital is funding to help citizens hold government spending to account, scrutinising budgets and social programmes and ensuring that they’re meeting the needs of the poorest. 

Closer to home, the IMF, UN, World Bank and OECD have all urged developed countries to make sure changes to their own tax regimes don’t damage those of developing countries. Yet the Finance Bill currently going through Parliament threatens to open up a major new loophole in the UK’s 'Controlled Foreign Companies’ rules, making it easier for multinational companies to shift profits into tax havens. ActionAid estimates this rule change is likely to cost poor countries £4bn a year, on top of nearly £1bn to the UK’s public finances annually. This flies in the face of the need to support developing countries’ efforts to become dependent of aid.

And at a global level, the fight against international tax avoidance has slipped steadily down the agenda of the G8 and the G20 over the last 18 months, despite its potential to stabilise public finances in the developing and the developed world alike. The "post-2015" re-think is an opportunity to put it back on the agenda. At stake is the future of the fight against poverty.