More than 1.2 billion people are living on less than $US1.25 ($A1.35) a day and 2.4 billion on less than $US2 a day, UN Secretary-General Ban Ki-moon says.

Ban told the UN observance of the International Day for the Eradication of Poverty on Friday at least 700 million people were lifted out of extreme poverty between 1990 and 2010 and he is determined to help the UN make “poverty history”.

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Since the beginning of the financial crisis in 2008, he said inequality has grown more pronounced and discrimination against women and girls remains “a blatant injustice”.

Ban warned that “entrenched poverty and prejudice and vast gulfs between wealth and destitution, can undermine the fabric of societies and lead to instability”.

The UN chief pointed to the Ebola crisis in west Africa, saying the disease is not only threatening health but economic progress and the inroads against poverty being made in the three hardest-hit countries, Liberia, Sierra Leone and Guinea.

Vigils have been held throughout the world. Photo: AAP

The observance coincided with the release of a UN report by international experts on financing sustainable development which cited research from the Brookings Institution showing about $US66 billion ($A71.41 billion) is needed annually to increase incomes of the poorest to $US1.25 a day.

Finnish Ambassador Pertti Majanen, co-chair of the experts committee, said government aid to developing countries is about double that amount.

The experts said trillions of dollars a year are needed to finance development that preserves the environment.

Annual global savings of $US22 trillion are sufficient to pay for such things as renewable energy and measures to mitigate climate change, the experts said.

The challenge, they said, is for countries to promote financial systems that give incentives to reallocating a percentage of savings to development programs, including combating climate change.

Majanen told a news conference institutional investors’ assets today are $US80-90 trillion, and only a very small percentage is used for development efforts.

He said a better dialogue with the private sector could open “huge possibilities” for greener investments to promote development.

World hunger falls, but 805 million still chronically undernourished- raise awareness for the eradication of #poverty worldwide #MDGMomentum — UNITAR (@UNITAR) October 17, 2014