The richest 1pc of people will own more than half the world's wealth by next year.
The combined wealth of the other 99pc will not match that of the elite, unless "staggering" levels of inequality are tackled, Oxfam has warned.
Political and business leaders gathering at the World Economic Forum in Davos are set to be challenged over the widening gap between the wealthiest and the rest.
A research paper released by Oxfam suggests the richest 1pc have seen their share of global assets rise from 44pc in 2009 to 48pc last year - with an average worth of $2.7m (€2.3m) each.
The wealth share of the richest 1pc is on track to exceed 50pc in 2016, the charity said.
Below the richest fifth, 80pc of the world's population own just 5.5pc of wealth - an average of $3,851 (€3,316) each.
This is equivalent to 1/700th of the average wealth of the richest 1pc.
Oxfam said the "very richest" of the top 1pc - the 80 individuals at the top of the 'Forbes' Billionaires list - have seen their total net wealth rise from $1.3trn in 2010 to $1.9trn last year.
The report added: "The wealth of these 80 individuals is now the same as that owned by the bottom 50pc of the global population, such that 3.5 billion people share between them the same amount of wealth as that of these extremely wealthy 80 people."
Last year, 1,645 people were listed as billionaires and Oxfam said the group was "far from being globally representative".
Almost 30pc are US citizens, and more than a third of them inherited some or all of their wealth, according to the report.
Oxfam International executive director Winnie Byanyima said: "Do we really want to live in a world where the 1pc own more than the rest of us combined?
"The scale of global inequality is quite simply staggering and despite the issues shooting up the global agenda, the gap between the richest and the rest is widening fast.
"In the past 12 months we have seen world leaders from President Obama to Christine Lagarde talk more about tackling extreme inequality, but we are still waiting for many of them to walk the walk.
"It is time our leaders took on the powerful vested interests that stand in the way of a fairer and more prosperous world.
"Business as usual for the elite isn't a cost-free option - failure to tackle inequality will set the fight against poverty back decades.
"The poor are hurt twice by rising inequality - they get a smaller share of the economic pie and because extreme inequality hurts growth, there is less pie to be shared around."
Ms Byanyima will call on leaders gathered in Davos to adopt a seven-point plan to tackle inequality.
Its measures include:
◊ Clamping down on "tax-dodging by corporations and rich individuals";
◊ Investing in universal free public services such as health and education;
◊ Introducing equal-pay legislation and promoting economic policies to give women a fair deal;
◊ Agreeing a global goal to tackle inequality.