Some of the 57 member nations say it is now time for the Organisation of the Islamic Conference to do something about the gap, though few expect to see major changes soon.
Economic solidarity is meant to be one of the key themes at the OIC's two day summit with price of oil now above $107 a barrel.
"Economic solidarity exists in several forms within the OIC but today it is not sufficient and the Dakar summit should be the occasion to make it better," said Mohamed Dowuidal, head of the economic mission at the Egyptian embassy in Dakar.
"The OIC includes countries with enormous differences in wealth and it is now important to devote time to solidarity that goes beyond normal state to state links," he told AFP.
Two years ago, the summit host, Senegal's President Abdoulaye Wade, called for the creation of a pan-African group of non-oil producers that would get a tax on the profit of the continent's oil producers. Little happened.
Today the OIC's main economic weapon is its Islamic Soldarity Fund for Development, thought up by Saudi Arabia's King Abdullah at a summit he hosted in 2005 and officially launched last year by the Islamic Development Bank, the OIC's financial arm, whose members include 11 of the world's 15 poorest states.
The fund, bankrolled mainly by Saudi Arabia and Kuwait, will eventually have $10bn.
The fund will again be raised at the summit.
OIC secretary general Ekmeleddin Ihsanoglu called last year for "greater effort" to be put into Muslim nations digging into their pockets to help each other.
Senegal's Foreign Minister Cheikh Tidiane Gadio called for the summit to become "a historic turning point" that will see "new forms of solidarity that attracts investment from Muslim countries to other Muslim countries."
"It is the OIC that has the biggest disparity between rich countries and poor ones," said Ali Sow, vice president of Islamic Solidarity Action, a non government group.
"This solidarity can only be developed through funds."
- AFP