It's Christmas time (nearly) and quite soon it will be impossible to switch on the radio without being bombarded by the preachy strains of a slightly shambolic Christmas song recorded 25 years ago in an effort to feed the world.

Band Aid's "Do They Know It's Christmas?", written in haste by Bob Geldof of the Boomtown Rats and Midge Ure of Ultravox, was unprecedented. Shocked by the BBC newsreader Michael Buerk's report of the famine in Ethiopia, which claimed a million lives, and the distressing footage of children with distended stomachs in a bleak African landscape, Geldof and Ure strong-armed some of the biggest names of the 1980s music scene into making the charity record.

Geldof, whose own career was on the decline, pledged that every penny would go to the cause. He even faced down Margaret Thatcher's government which initially refused to waive VAT on the single but later relented.

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So at dawn on a bleak 24 November, Ure and Geldof turned up at the London studio of the record producer Trevor Horn, which he had donated for 24 hours as he was not able to work on the track. The two musicians were armed with backing recorded the previous evening at Ure's home studio.

It was also the perfect news story, and the world's media were on hand as the biggest acts of the 1980s – Spandau Ballet, Duran Duran, George Michael, Sting, Bono and Adam Clayton of U2, Paul Young and Bananarama – turned up to record their contributions. Geldof even insisted that Boy George fly in from America – he turned up at six in the evening. Ure and Geldof worked late into the night mixing the record, before Geldof went on the radio the next morning to plug it.

The resulting single, bolstered by media attention, sold a million copies in the first week of its release in early December 1984, and went on to be the fastest-selling UK single of all time.

It stayed at No 1 for five weeks, clocking up sales of 3.5 million, the biggest selling UK single until Elton John's Princess Diana tribute, "Candle in the Wind", in 1997. Eventually, it raised £5m for famine relief. Two other versions – 1989's Band Aid II and 2004's Band Aid 20, which both also hit No 1 – raised millions more. There was more money from the Live Aid concert in 1985 and 2005's follow-up, Live 8.

In all, Geldof and Ure's wheeze – copied in America as USA for Africa – put more than £150m into famine relief. The Band Aid Trust still has an income of about £2m a year, which is spent in Ethiopia, Sudan, Uganda, Eritrea, Somalia and Nigeria.

It was meant to be the song that changed the world. Only it didn't. Twenty-five years on, famine stalks Ethiopia and the Horn of Africa again. As The Independent on Sunday reported in August, millions of people in the Horn of Africa are facing malnutrition and starvation in the worst food shortages since 1984.

The United Nations warned in June that as many as 6.2 million people in Ethiopia will need some kind of food aid in the next few months. But the true figure of those with insecure food supplies could be as high as 13.7 million. Twelve million Ethiopians received food from donor countries last year – Britain is the second biggest donor – most of it through the United Nation's World Food Programme. Aid agencies fear for this year's harvest because of poor rain and critical water shortages.

The government in Ethiopia, however, remains reluctant to use the word famine. Earlier this year, its prime minister, Meles Zenawi, said there was no danger of famine this year. Ethiopia's ambassador to Britain, Berhanu Kebede, insisted the problem was being tackled. "We are addressing the problem. Food is in the pipeline," he said.

Ethiopia doesn't want attention distracted from its achievements in education, trade and infrastructure. But its population has doubled to 80 million since 1984, and its rural economy is said to be less productive than that of medieval England.

"The [Ethiopian] government has just got to embrace the crisis and not be frightened of the statistics," Gareth Thomas, a minister with the Department for International Development, said. "It is different from 1984, but there's still huge need. There's got to be a recognition that if we are going to stop children from being malnourished and keep people alive, we have to have accurate information."