Let's say it takes six minutes for you to read this column.

Between now and when you turn the page, 26 children somewhere in the world will have died of malnutrition. Scale it up and by 2025 a billion people, one-eighth of the world population, will be trapped by hunger, their growth stunted, their life chances shrivelled.

It wasn't meant to be like this. The first Millennium Development Goal was to halve extreme poverty and hunger by 2015. We're way off target. The absolute number going to bed hungry has been falling since 1990, despite a burgeoning global population, but the rate of change is glacially slow and in 2012, for the first time in many years, the number of hungry children rose, according to Save the Children.

Climate change, which could halve the crop yields of some developing countries, will make things a lot worse, if we don't help.

That's why Oxfam and 100 other leading British charities and faith groups, backed by Desmond Tutu and billionaire Bill Gates, have got together to form the biggest coalition since Make Poverty History in 2003, which did so much to raise the profile of global poverty. It's based on a simple premise: if the world grows enough food for everyone (which it does), hunger is morally indefensible. The issues may be complex but there is a powerful simplicity about the "Food for Everyone If" campaign. And the sight of cheering Glasgow schoolchildren gathered around giant inflatables of the letters IF yesterday, somehow did kindle a sense of hope in me.

In theory, 2013 provides a unique opportunity. The UK could use David Cameron's G8 presidency to attack the root causes of extreme poverty.

Yet the last few days' headlines illustrate how hard this issue will have to fight to gain attention. Yesterday's launch was overshadowed by the Prime Minister's dramatic EU speech. And events in the Algerian desert have already prompted him to declare that tackling terrorism will be his "number one priority at the G8".

It's too easy not to think about world poverty. About 14% of people go to bed hungry every night. Imagine if they lived in your community. In mine, which is about 2000-strong, that would be about 280 thin, ragged, hungry people. Of course, they wouldn't starve because of all the perfectly good food we chuck in our bins every day but life doesn't work like that. My mother used to chide me in the 1950s with talk of African children eagerly devouring my leftovers and I fondly imagined posting the odd fish cake or sausage to a skinny kid in Nigeria. I didn't confront the grotesque inequality and unfairness of life in a global food market rigged against the interests of the poorest until I visited a primary school in northern Kenya nine years ago. Every day pupils fainted from hunger after walking miles on empty stomachs to reach their classrooms. Hungry children can't learn.

Today all those pupils get a free meal, thanks to a British charity, and their exam results have zoomed up the national league table. Some go on to secondary school and a few even to university. One day they will help transform their communities. But this campaign isn't ultimately about food aid but about giving the world's poorest people the power to feed themselves.

That's why the first big If is: "If governments keep their promises on aid". Despite mean-spirited campaigning from some right- wingers, Britain looks to be on course to become the first G8 member to achieve foreign aid of 0.7% of national income, though nobody will count that chicken until they see it in the Queen's Speech. Mr Cameron must use his G8 presidency to chivvy other members into keeping the foreign aid commitments they made at Gleneagles in 2005 and shaming backsliders.

In the first instance that money is needed to stop children dying of malnutrition but ultimately it must fund self-help by offering modest grants to small farmers to improve their productivity and access to markets. At yesterday's launch I ran into the Rev John Riches of Just Trading Scotland, who said he hoped to double the yield (and hence the incomes) of Malawian farmers who sell their Kilombero rice to him. "They just need better quality seed," he said.

The UK must also honour its commitment to support developing countries to adapt to meet the challenges of climate change, in addition to the aid pledge.

The second If is about forcing governments and investors to be open about their dealings. If developing country governments do not publish their budgets, poor communities cannot check they are keeping their promises. Just as important is the third If: "If governments stop big companies dodging tax in poor countries", which lose three times more from tax evasion than they get in aid. That's why it's so important to tackle the tax havens where corporations hide their profits.

The final If is about stopping small farmers being forced off their land. The rate of the current land grab is alarming. It accounts for an area the size of London every six days. Developing countries desperately need private investment like that of Scottish entrepreneur Sir Ian Wood, who has just bought a majority shareholding in two Rwandan tea factories, opening the possibility that thousands of smallholders will soon earn back 70% of the price of their tea, rather than the current 25%. Today, too often locals without proper rights are forced off their land and foreign investors export everything they produce. Biofuels bear much of the blame.

The sheer mind-boggling complexity and interconnectedness of these issues can induce defeatism. Small triumphs like Martha's Meals and fair trade chocolate and bananas show how determination, imagination and goodwill can create virtuous circles. If the world's poor lived at the end of our gardens, every MP, MSP and MEP's mailbox would be stuffed with demands to end world hunger. That's why the most powerful supporter of the If campaign isn't Bill Gates or Sir Ian Wood. It is you.

www.enoughfoodif.org/scotland.

Anne Johnstone sits on the advisory board of Oxfam Scotland.

Iain Macwhirter is away.