The G20 are currently meeting in Seoul giving the international community a chance to put tackling global poverty firmly at the top of the agenda. With the Millennium Development Goals off track, a difficult global economic climate and many countries backtracking on their aid promises, that is more important than ever.

Traditionally, the G8 has served as the principal forum to discuss development issues, but as the global balance of power shifts it must also be a central part of G20 discussions. The South Korean government has admirably tried to make sure that is the case, but so far international development has been overshadowed as an issue at this summit. The agenda is likely to be dominated by how to maximise economic growth, but world leaders must also demonstrate their commitment to a development agenda, recognising that laying the foundation for a fair and sustainable world economy is a central part of any growth agenda. While growth is of course an important part of helping developing countries emerge from poverty, it is not enough on its own.

The focus of global development efforts at this summit appear to be shifting away from financial aid. Nobody argues that aid on its own is the solution to global poverty but it is an integral part. In many cases, without it, developing countries would be unable to build up the necessary infrastructure and public services which will ultimately allow them to pursue effective growth strategies. At this G20 there is a real danger that aid will fall off the agenda altogether, letting those countries who are failing to keep their international aid promises off the hook.

Britain is in a unique position to ensure that is not the case. Following Labour's term of office Britain is one of the few G8 countries that is on track to meet its aid promises and we have a reputation as a global leader. Not only must David Cameron make sure that continues to be the case, but he must take the lead to ensure that the moral capital that the UK has built up on this issue does not fade away.

Yet, so far, the UK government is failing to make the convincing case for aid. In his speech at the G20, David Cameron did not even mention international aid. His actions at the last meeting of the G8 in Canada were equally disappointing as he stood by and did little to save the Gleneagles targets which we fought so hard for in 2005. That stands in stark contrast to the international leadership on development that the UK displayed under Labour. This included successful efforts at the London summit in 2009 to take concrete steps to help benefit the world's poorest countries.

We welcome the commitment that the government made in the spending review to protect the aid budget; making sure we are on track to meet the target of spending 0.7 per cent of our gross national income on aid from 2013. However, in order to send a clear message to the rest of the world that Britain is not a country that breaks its promises, and to calm fears that the 30 per cent increase between 2012 and 2013 their plans demand will not be delivered, they need to go one step further. We are calling on them to bring forward the legislation that they have promised to put that pledge into law as soon as possible. So far they have refused to set a date. If we are really to believe that they will meet their promise then we need more than just warm words.

The government should be proud that they are protecting our aid budget not acting as if they have a shameful secret to hide. At a time when Conservative backbenchers and a vocal section of the national media are lining up to denounce the decision to ringfence our aid budget, it is more important than ever that the government stands up and takes on those critics and makes the argument for aid both here and abroad.

Aid is working. There are few things that cost so little but make so much difference. In the last 50 years, child deaths in the developing world have been cut by more than half, polio has been practically eradicated and, 2010 compared to 2009, 98 million fewer people are going hungry. These are not just statistics, they are millions of lives saved and transformed thanks to effective international development efforts. It is up to all of us who care about building a fairer world to make that case and to ensure that the world's poorest are not forgotten.

Fighting global poverty is right for humanitarian reasons. We all have a responsibility not to turn away when millions are suffering. But not only is it morally right, in an increasingly interconnected world it is also in our national interests. Conflict, disease, insecurity and climate change will have repercussions for us all and tackling them must be a global responsibility.

At this G20 we need leadership from the government. David Cameron has an opportunity to show that he is ready to carry on the UK's leadership on international development - an international reputation that came because we were never just willing to settle for the bare minimum. Actions speak louder than words and that's why it is time for David Cameron to take the lead and make the case for a continued compassionate role for Britain in the world.

There are many actions the G20 could approve that would benefit developing countries if there is enough political will - a push to complete the Doha trade round, growth policies that tackle inequality and identifying sustainable finance sources to tackle climate change but aid must not be forgotten. This is the first time the G20 is taking place in Asia - a continent with some of the fastest growing economies in the world but also with some of the poorest people. There could be no better place for David Cameron to send a clear message about the importance of Britain's continuing international aid commitments.