In 2005, wealthy nations vowed to make poverty history. As their leaders prepare to meet in the UK again, the task is unfinished – and they are under pressure to tackle their own problems first

It was a different era. The biggest beasts in international politics were padding around Edinburgh as stock markets soared and the UK basked in the glory of winning the right to host the 2012 Olympic Games. Debt was something poor countries owed to rich countries, and the rich countries were doing just fine.

The Gleneagles G8 summit in July 2005 has come to be seen by many development experts as the most ambitious of its kind. Groups such as War On Want have been highly critical of the G8's ambitions and achievements, but in PR terms, the summit was a clear triumph.

Building on the success of the Make Poverty History campaign, one of the biggest grassroots movements the world had seen, the likes of Tony Blair, George W Bush, Jacques Chirac, Gerhard Schroeder, Silvio Berlusconi and Vladimir Putin pledged to transform Africa's fortunes and, in the words of the summit's concluding communique, "build the successful future all of us want to see".

The Live 8 event that preceded the summit focused the world's attention on aid and development and, for a while, seemed to make the subject cool. U2 and Paul McCartney opened a concert beamed around the world. Pink Floyd played together for the first time in almost a quarter of a century. Bob Geldof, the Live 8 founder, performed the Boomtown Rats' I Don't Like Mondays.

Eight years later the musicians have fared better than the politicians. With the exception of Putin and Berlusconi, the big beasts have gone. But Bono and McCartney are still going strong, while Geldof is reforming the Boomtown Rats this summer. They will perform to a transformed world. The banking crisis of 2008 washed away the world's faith in its financial institutions. Three years after the G8 countries agreed at Gleneagles to drop $40bn owed by some of the most indebted countries to the World Bank, it emerged they themselves had been living beyond their means.

Now, another summit commitment, agreed by the UK and other European countries – to turn 0.7% of their gross national income into overseas aid – is under intense scrutiny as angry voters, and a sizeable number of Tory MPs, question the wisdom of making a pledge many think their governments cannot afford. Ukip's success in Eastleigh, knocking the Tories into third place, is a reminder that a significant proportion of voters prefer their parties to be more inward-looking.

It has been estimated that the UK is contributing 0.55% of its income to aid, making it the most generous donor in the G8 and on course to fulfil its commitment by 2015. France is contributing 0.42% and the US 0.2%, while Italy and Japan each contribute 0.17%.

Given such discrepancies, questions have been raised about the government's commitment to introduce legislation that will ensure its 0.7% commitment is fulfilled. Aid groups fear these doubts are creeping into government thinking. "Later this month George Osborne must confirm that Britain will assign 0.7% of national income to the aid budget from 2013 and, in line with the coalition agreement, enshrine it in law as soon as possible," said Joseph Powell, senior policy manager at One, the anti-poverty charity co-founded by Bono.

In a bid to appease his critics, David Cameron has signalled that some of the aid budget could be diverted to UK peacekeeping operations, a boost for the armed forces. But he has little wriggle room as Britain prepares for this summer's G8 summit at Lough Erne in Northern Ireland, the first it has hosted since 2005.

"The world has changed," acknowledged Justin Forsyth, chief executive of Save The Children and a former Downing Street adviser who worked on the Gleneagles summit. "At the time, the G8 was a very strong body … but a lot of leaders are now focused on their domestic agendas."

Forsyth gives the 2005 summit a "seven out of ten" mark: "We've made more progress in alleviating poverty than at any other time in history." He recalls with fondness how, as Bush was flying in on Air Force One, the UK persuaded the US to back an agreement pledging universal access to Aids drugs. "Then we went around every other government and told them they were the only ones holding out. We bounced them all."

But did Gleneagles really deliver? The Millennium Development Goals (MDG), which set specific targets for improving conditions in the world's poorest countries and helped to frame the Gleneagles commitments, expire in 2015. If there is to be consensus on what should replace them, gauging their impact is crucial.

Summit in Sight, a report by One to be published this week, offers a detailed analysis of what has been achieved so far. Notable successes highlighted in the report include an 18% reduction in child mortality in sub-Saharan Africa, a 9% drop in people living on less than $1.25 a day, a 547% rise in internet users, access to potentially life-saving vaccines for 5.4 million more people, an extra 21 million children in schools and a million fewer new HIV infections.

Some will question how much these successes can be attributed to Gleneagles. But, writing in the report, Kofi Annan, the former UN secretary general, says: "The Gleneagles summit of 2005 is rightly remembered as a high point for the G8. This report shows that the increases in aid and debt relief have, in the last eight years, helped support African leadership. The fact that 21 million more children are in school than at the time of Gleneagles, and 5.4 million more people are on anti-Aids drugs, is a cause for celebration and for the G8 to continue their supporting role."

Bono also talks up the achievements. "If the trajectory continues, look where the amount of people living on less than a $1.25 a day gets to by 2030 – the zero zone," he told a Ted conference in Long Beach, California, last week.

But there have been notable failures. The One report acknowledges that "the G8's broad failure to create a better trade environment for African countries, notably the continuing gridlock of the Doha round of trade negotiations, stands out as one of the most clearly missed Gleneagles commitments".

Sanitation is a cause for concern. The One report notes: "Sub-Saharan Africa has fallen far behind global progress and is currently not on track to achieve the MDG target; in fact, over 40% of all people globally who lack access to drinking water live in sub-Saharan Africa."

And malnutrition rates remain stubbornly high, largely as a result of a failure to deliver effective food security plans. The One report says: "The G8 has made repeated promises to support CAADP [Comprehensive Africa Agriculture Development Plan]. Yet country plans are only about 60% funded."

The failures will give succour to the increasingly influential lobby that is calling into question the philosophy and efficacy of aid. Writers such as Cameron's former speech writer, Ian Birrell, argue that Africa is not the continent it was a decade ago. It has a burgeoning middle class and a wealth of mineral resources. Aid not only risks furthering a dependency culture, they argue, it is also increasingly unnecessary.

Writing in the Observer last year, Birrell argued that "too many people remain locked into stale narratives of Africa as a land of suffering in need of our salvation" and suggested that the "continent is on the edge of economic take-off similar to those seen so dramatically in China and India".

As the One report notes: "Sub-Saharan Africa is also very different to that of 2005. There has been a significant rise in the volume of domestic revenues, from $174bn in 2005 to $341bn in 2011."

The debate swirling around aid in a time of austerity is a key reason why this year's summit will focus more on issues such as improving transparency and clamping down on tax avoidance, rather than increasing development budgets. Bono talks of transparency being a "vaccine" against corruption. Powell suggests that "giving citizens the information they need on extractive industries and government budgets" could be a "game changer".

But today's leaders of the G8 countries may not be so interested in the arguments of rock stars or development experts. They have their own problems.

• Visit One's website here

• This article was amended on Sunday 3 March 2013. The article said Justin Forsyth recalled how the UK persuaded the US to back an agreement pledging universal access to drugs. To clarify, this should have said Aids drugs. This has been corrected.