What do you call a frozen fish factory built by Scandinavians in the desert of northern Kenya, which closed shortly after it opened?

Yet another bungled Western intervention in Africa, say the aid sceptics. And that’s no joke. In my ten years in international development, after a career in the private sector, I’ve heard plenty of stories like that – about how aid fails to deliver, how it engenders a dependency culture and, above all, how it doesn’t improve the lives of struggling families in Africa.

It’s just dead aid, according to the Zambian former Goldman Sachs banker who wrote the influential book of that name earlier this year. Dambisa Moyo’s criticisms have struck a chord in these cash-strapped times: why should the UK be chucking money down a drain, thousands of miles away, when it could be better spent at home?

Amid a fierce party political dispute over spending cuts, the same questions are being asked of the Tories. David Cameron’s pledge to ring-fence international development spending – the only area to be saved from cuts apart from health – looks, in the words of one columnist, “increasingly bizarre”. The economic climate sharpens Tory rank and file criticism that aid is anti-business, and help would be better delivered through personal or corporate philanthropy.

The third annual trip to Rwanda for 100 Tory MPs and candidates will no doubt be a formative experience for those involved. But, despite these visits, a recent survey of Tory candidates showed, worryingly, that only a tiny 4 per cent believed the aid budget should be protected from cuts, compared with 23 per cent for schools and 39 per cent for defence.

So, as the party prepares to launch its Green Paper on international development today, why should Mr Cameron and his team reaffirm UK pledges on aid? Well, no other recent issue — apart from the Iraq war — has had the power to mobilise public opinion in the same way. Who can forget “Make Poverty History” in 2005? That was when international development went mainstream; a quarter of a million turned out on the streets of Edinburgh and many more sported the iconic white band of support throughout that summer.

Nor was it, as critics claimed, a celebrity-driven flash in the pan. A couple of weeks ago at Glastonbury, Save the Children signed up 20,000 new supporters – double our target — to our child survival campaign. There was no media fanfare, just good-tempered festival-goers queueing to make their thumbprint on our petition, many of them the young, globally-aware citizens politicians need to woo.

Second, if he wins, Mr Cameron will inherit a record in which Britain really can claim to be the global leader. Last September’s United Nations summit in New York, was a febrile affair as Wall Street buckled under the economic crisis. But Gordon and Sarah Brown were celebrated as champions by other leaders who recognised their commitment to education and maternal health and acknowledged the real difference this leadership makes in the world.

Over the past decade, Britain has used its own aid budget to lever much larger amounts from the G8 countries. It would be perverse for any British prime minister to give up this position of global leadership. It is hard to think of a single other area where Britain’s global standing can be achieved at so little cost: £9.1 billion next year rising to 0.7 per cent of GDP in 2013.

Third, and most importantly, aid can deliver tangible successes — but charities tend to do a terrible job of getting this message across. We have to realise that people are intrinsically suspicious of “world-changing paradigms”. I certainly was when, in 2000, having just come from running a Thomson technology business in the US, I attended a global conference in Senegal, aimed at getting every child in the world a basic, decent education. I remember thinking the promises couldn’t possibly be matched by reality. A staggering 140 million children were out of school: it would, I thought, take a generation of superhuman effort to dent those figures.

But guess what? Less than a decade later, thanks largely to the British-led Fast Track Initiative — a deal that committed rich countries to ensure that no robust national education plan should go unfunded — the number of children out of school has almost halved, down to 75 million. That success helps Save the Children to win support for its drive to educate the hardest-to-reach children: we are enrolling the equivalent of two schools of children a day in states affected by conflict.

International development, supported by smart aid, is in our interests, doesn’t cost a fortune, and enjoys public support. And cheap jokes about 1980s failed aid projects aside, doing our bit to save children’s lives and to help them to grow up healthy, educated and safe is simply the right thing to do. Political leaders can’t duck this challenge: Britain has made promises to the poorest people in the world. We must keep them.

The author is chief executive of Save the Children

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