The inequality report, released just hours before world and business leaders meet at 2018's World Economic Forum in Davos, Switzerland, says last year saw the biggest increase in billionaires in history - widening the gap between rich and poor even more.
The increase in wealth for billionaires - 762 billion USD over the year - is enough money to end extreme poverty across the world seven times over, the report says.
The charity is calling on leaders at Davos to crack down on tax avoidance, increase levels of taxation for the wealthy and close the gender pay gap to create a more "equal society".
