World leaders on Friday pledged to commit $20bn over three years for a “food security initiative” to develop agriculture in poor countries, but aid agencies responded with scepticism, pointing to a chain of broken promises and a habit of switching around existing budgets.

The Group of Eight summit of rich countries in L’Aquila, Italy, had aimed to pledge $15bn (€10.8bn, £9.3bn). Ministers described how a last whip-round before delegations left came up with an extra $5bn to make a bigger headline ­figure. “There is an urgent need for decisive action to free humankind from hunger and poverty,” said a joint statement of 40 heads of government and international organisations, including the G8.