JERUSALEM (Reuters) - Israelis and Palestinians could all be twice as rich as they are today if conflict had not continued throughout the peace process of the past two decades, an international think tank said on Wednesday.

The Strategic Foresight Group, an India-based body that says it has advised governments, said Israel`s offensive in the Gaza Strip made the findings of its report `Cost of Conflict in the Middle East,` issued on Wednesday all the more urgent.

Income per head for both Israelis and Palestinians would have been almost double what it is now, it found. Israelis earn on average almost 20 times more than Palestinians.

`The current crisis in Gaza demonstrates again the need to consider the long-term costs of our actions,` the group`s head, Sundeep Waslekar, said in a statement.

More than 1,300 Palestinians were killed in Israeli air and ground strikes in the Gaza Strip, launched on December 27 with the declared aim of ending rocket attacks. Thirteen Israelis were killed during the three weeks of fighting.

Israelis and Palestinians began peace talks in Madrid in 1991 that led to Palestinian self-rule in parts of the West Bank and Gaza Strip, which Israel had occupied in a 1967 Middle East war. Palestinians began an uprising in 2000.

`For Israel, peace since 1991 would have meant an average per capita income of $44,000 (31,511 pounds) by 2010 rather than $23,000. For Palestinians, per capita income would have been $2,400 by 2010 rather than $1,220,` the statement said.