CANNES, France — Leaders of the world’s biggest economies were scrambling today for ways in which they could help Europe ringfence its raging debt crisis without exacerbating their own money troubles.

But as on the first day of their summit, much attention in the swanky seaside town of Cannes in southern France will center on Greece, where Prime Minister George Papandreou faces a confidence vote in Parliament.

The abandonment of the referendum pledge over last week’s rescue deal might have eased some market concerns over a disorderly Greek debt default but the country remains mired in a crisis that could see the Socialist government fall and early elections called.

On the final day of their get-together, the leaders of the Group of 20 economies will be looking at ways to boost the firepower of the International Monetary Fund, the institution that was set up as the lender of last resort for struggling governments after World War II.

With their own finances already stretched from bailing out Greece, Ireland and Portugal — and traditional allies like the United States wrestling with their own problems — eurozone countries are looking to the IMF to use its resources and rescue experience to help prevent the debt crisis from spreading to large economies like Italy and Spain.

But within the IMF, the powers have shifted.

Until two years ago, the IMF — dominated by the traditional powers in Europe and the U.S. — mostly applied the painful adjustment programs that are attached to its financial lifelines to poor and emerging economies in Asia, Latin America and Africa.

Now, it’s growing powers like China, Brazil and South Africa that have to decide whether helping Europe is a worthy investment.

Last week, eurozone leaders decided to boost the firepower of their $606 billion bailout fund by seeking financing from outside investors. Those additional resources could then be used to buy up bonds from wobbly countries like Italy and Spain and help them and others recapitalize banks hit by the turmoil on the markets.

Yet cash-rich countries like China, Russia and Brazil quickly made clear that any investment from their side would have to be channeled through the IMF. That would ensure that their loans come linked to strict economic conditions.

European Union officials said one option that has emerged from talks in Cannes is for the IMF to set up a sort of trust fund that would be overseen by the fund but not use any of its own resources.