LONDON (REUTERS) - Setting the stage for this month's G-8 summit of rich industrialised countries, British Prime Minister David Cameron on Saturday called for fresh approaches to help eliminate malnutrition and hunger among the world's poorest children.

As donors, charities and officials gathered for Saturday's Nutrition for Growth event, up to 45,000 people rallied in London demanding global leaders take specific steps to tackle hunger when they meet in Northern Ireland later this month.

Charities have linked poverty and hunger in developing countries to tax dodging by some global corporations - a topic at the heart of Britain's G-8 presidency.

Seeking to portray Britain as a defender of the global poor, Mr Cameron proposed a target of saving 20 million children from chronic malnutrition by 2020.

This echoes an earlier goal by the Group of Eight, set in 2000, to halve the proportion of people living on less than US$1.25 a day by 2015 and other similar global targets, where progress has been mixed at best.

"We will never beat hunger just by spending more money or getting developed nations and philanthropists to somehow 'do development' to the developing world," Mr Cameron said.

"It has to be about doing things differently. Different in terms of business. Different in terms of science. And different in terms of government."

At the event, governments and development agencies made commitments of up to US$4.15 billion (S$5.18 billion) to tackle undernutrition up to 2020 in a deal dubbed the Global Nutrition for Growth Compact.

Other initiatives included improving the nutrition of pregnant women and young children, and saving children's lives by increasing breastfeeding and improving the treatment of severe malnutrition.

In his address, Mr Cameron said he was proud of Britain's commitment to spending 0.7 per cent of gross domestic product on development aid despite a period of austerity that has forced his government to cut many parts of the national budget.

In London, Microsoft founder Bill Gates and other prominent figures joined a festival-like rally in sunshine in central London's Hyde Park in support of the cause. British media reported said up to 45,000 people had gathered.

"We need to be more generous and we need to pay attention to what's going on in these poor countries," Mr Gates told the BBC.

"If they were living in our neighbourhoods, obviously we would reach out and help them, and that's why today's event is so important."