No one likes to think of themselves as a fair-weather friend. Being flaky in a crisis is not, after all, an attractive quality.
But much as they might try to hide it when they meet in Canada this week, the world's richest nations are proving themselves to be just that to the world's poorest people: unreliable at a time when they are reeling from the economic crisis, climate change and food shortages.
Five years ago, during the good times and amid much fanfare, the G8 met in Gleneagles and promised to "Make Poverty History" -- to cancel developing countries' debt, make trade fairer and increase aid to the poorest countries by $50 billion.
But while great progress has been made in ditching the debt, progress toward fairer trade rules have stalled completely and the commitment to increasing aid has not survived the economic crisis.
By 2008, when I attended the G8 summit in Japan as an Oxfam ambassador, some countries were already off-track to meet their aid promises. But little did I imagine that when promises became due two years later, the world's richest economies, with a combined national income of well over $30 trillion, would have been barely halfway toward their aid targets, falling short by a whopping $20 billion.
I'm going back to the G8 this year to do what little I can to put pressure on Presidents Sarkozy and Berlusconi and Chancellor Merkel, in particular, to live up to their promises. And at the G20 that follows I will be campaigning for a Robin Hood Tax on the financial sector to meet the new challenges facing poor countries.
Because the fact is that aid is needed now more than ever. The World Bank estimates that by the end of 2010, 64 million more people will be living in poverty, surviving on less than $1.25 a day as a result of falling trade, investment and capital flows.
Africa faces a $65 billion budget black hole which, without outside help, will inevitably lead to cuts in schools and clinics that are vital to tackling poverty in poor countries.
Millions of people's lives and livelihoods are under threat from changing weather patterns and natural disasters linked to climate change.
It seems to be fashionable to question whether aid really does improve the lives of poor people. Reading much of the popular press you could be forgiven for thinking most gets lost to corruption or does little to help the people who receive it.
This could not be further from the truth. Aid is not perfect and fighting corruption remains important for all those who want to see currently poor countries prosper. But the evidence that aid works is overwhelming.
The successes can be seen in the statistics: maternal deaths have fallen worldwide, from over half a million a year in 1980 to less than 350,000 in 2008; in the past decade, more than 33 million primary schoolchildren have moved from the field or factory to the classroom; and more than three million people living with HIV now have access to the anti-retrovirals that will keep them alive, an increase of almost 50 percent since 2006. None of these would have been achieved without increases in aid.
But the personal stories behind the headline figures are far more compelling. Especially if, like me, you have had the fortune to hear them firsthand from the people whose lives have been transformed.
When I visited Tanzania with Oxfam in 2007, the charming and humbling villagers in Engare Sero told me how aid had changed their lives. Aid had paid for a grain bank so they no longer had to endure a 10-day round trip for a single bag of maize. Without outside help, they told me, they would be dead.
It is shocking that people in poor countries continue to die because of dirty water, because of lack of basic medicines and because they do not have enough food to eat.
Every hour around the world 40 women and girls die in pregnancy and childbirth. They do not die because they are feckless, lazy or stupid, but because the nearest hospital is often 100 miles away or they cannot afford to pay for treatment. The G8 has a responsibility to live up to its promises and help these mothers-to-be and one in seven children in Sub Saharan Africa who die before thief fifth birthday.
It would cost about $1bn to save the lives of one million of these children. Over time, the missing $20bn-a-year would be enough to do that plus meet the Millennium Development Goals of halving the number of people without access to clean water and ensure every child gets a primary education.
Only the UK can claim to be close to meeting ambitious promises to the poor. France, Germany, Italy and Japan are largely responsible for the missing billions but the US and Canada deserve to share the criticism. Meeting (or in Canada's case getting close to) their pledges counts for less when the promises they made to the poor were so paltry. All three are miles away from delivering the longer-term aid target of 0.7 per cent of national income needed to deliver the MDGs.
Canada is also guilty of blocking progress towards a tax on the financial sector that could raise hundreds of billions of dollars to help pay back poor countries for the damage they have suffered as a result of greed in the trading rooms of bank and hedge funds.
Taxing the financial sector not only offers rich countries a chance to meet their obligations to the poor without squeezing ordinary taxpayers. It would help rich countries balance their own budgets and protect services poor people at home rely on.
If the G8 leaders are not prepared to open their own wallets to help the poor in a time of crisis, then surely the least they can do is make those who caused the crisis pay a tithe for those who now suffer as a result.