Metaphors may not have been in the mind of Silvio Berlusconi when he summoned the leaders of the world’s most advanced states to survey the battered planet from the scene of an earthquake.

A field of ruins seems an apt venue, though, as presidents Obama, Sarkozy and Medvedev, along with Gordon Brown and the rest of the Group of Eight, gather today in the Italian town of L’Aquila to seek ways to rebuild, feed and clean a damaged world.

The Italian Prime Minister, whose exotic private life has clouded his turn in the club chair, wants the summit to reflect hope and recovery. He has summoned an extra four dozen other leaders and international figures — representing 90 per cent of the world economy, he boasts — to commune over climate change, food security, trade and global revival.

Italy has, however, set a poor example, falling far behind all the other rich nations in keeping earlier G8 promises to help Africa. When it comes to who has the moral and political authority, Mr Berlusconi is likely to be overshadowed by Mr Obama.

The G8 will endorse goals for fighting hunger, curbing carbon emissions and promoting growth. Ambitions for L’Aquila, however, are being undermined by its overambitious scale, a largely lame cast of leaders and a sense that the business is now being done elsewhere — by the 20-strong group of nations that was convened last year to rescue the world economy.

The rise of the G20 is sidelining the club of industrialised democracies that opened when President d’Estaing of France invited five fellow leaders for a fireside chat in a chateau in 1975.

This year only Mr Obama and Mr Sarkozy enjoy full political clout. Mr Berlusconi’s extracurricular activities embarrass his fellow leaders; Japan’s Taro Aso is not expected to survive a general election in September; Mr Brown is unlikely to represent Britain at next year’s summit. Angela Merkel, the German Chancellor, is respected but also faces a battle for re-election in the autumn, while Stephen Harper of Canada cuts little international dash and, in Russia, President Medvedev is deemed to be subordinate to Vladimir Putin.

President Lula da Silva of Brazil stuck the knife in before a pre-G8 session in Paris with Mr Sarkozy. “The G8 no longer has any raison d’etre, except for debating subjects other than the big economic picture,” he said. His point will be brought home in L’Aquila tomorrow when Mr Obama chairs a parallel group he has convened on climate change. This Major Economies Forum on Energy and Climate includes the G8 plus Australia, Brazil, China, India, Indonesia, Mexico, South Africa and South Korea.

Mr Obama, reversing recent US policy, wants a framework to succeed the 1997 Kyoto Protocol, which will expire in 2012. Mr Brown and Mr Sarkozy also agreed this week on the need for firm pollution targets in the medium term, which should be set at a UN climate change conference in Copenhagen in December.

The Americans are also making the running over efforts to secure food for poor countries: Washington wants the G8 to commit $15 billion (£9 billion) for agricultural development. Robert Zoellick, the President of the World Bank, has written to the G8 warning of growing hunger if they let up in efforts to restart the economy. “2009 remains a dangerous year. Recent gains could be reversed easily,” he wrote.

Mr Brown and Mr Sarkozy said in Evian on Monday that the danger was not over and they deplored backsliding in some countries and among bankers over the need to rekindle the economy. Their words were directed at reluctant lenders and at Germany, where Ms Merkel is campaigning for a quick return to fiscal prudence.

The British Prime Minister is also likely to embarrass his host with plans to name countries that have failed to meet their commitments on aid to the developing world.

Mr Berlusconi has already been shamed publicly by Bob Geldof over his country’s aid record.

Differences within Europe and with the US will also surface over protectionism and the need to restart the Doha Round of world trade talks. According to the World Bank, members of the G20 and several other countries have implemented 47 measures that restrict trade since the crisis began. The G8 powers are accused of damaging the poorer countries with tariffs on their farm products.

Defenders of the G8 argue that it is a useful workshop for aligning ideas and floating intiatives — and that it was never supposed to produce hard deals. This year, the focus will be on Iran and North Korea, with the hope of drawing Russia and China into Western efforts to put pressure on regimes that present a nuclear threat.

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