In a report released ahead of this week's annual meeting of the international elite at Davos in Switzerland, Oxfam said the top tier had seen their share of wealth increase from 44 percent in 2009 to 48 percent in 2014.
On current trends, it will exceed 50 percent in 2016.
The charity's executive director, Winnie Byanyima, who is co-chairing the World Economic Forum meeting in Davos, said an explosion in inequality was holding back the fight against poverty.
"Do we really want to live in a world where the one percent own more than the rest of us combined?" she said on Monday.
"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."
Oxfam said it would call for action to tackle rising inequality at the Davos meeting, which starts on Wednesday, including a crackdown on tax dodging by corporations and progress towards a global deal on climate change.
The richest 80 individuals in the world had the same wealth as the poorest 50 percent of the entire population, some 3.5 billion people, Oxfam said. This was an even bigger concentration at the top than a year ago, when half the world's wealth was in the hands of 85 of the ultra rich.
Members of the top 1 percent had an average wealth of $2.7 million per adult, Oxfam said.
The bulk of the world's remaining wealth was owned by the rest of the richest fifth, while the other 80 percent shared just 5.5 percent of the pot, equalling an average wealth of $3,851 per adult, it said.
Oxfam used data from the Credit Suisse Global Wealth Datebook, 2013 and 2014, and the Forbes' billionaires list to compile its research. — Reuters
