Growing inequality means that the world's 62 wealthiest people own as much as the poorest half of the planet's population, some 3.6 billion people, according to a new report from Oxfam.
The richest 1%, around 73 million out of the world's 7.3bn people, now own as much as everyone else put together, said the report, published ahead of the annual World Economic Forum of global political and business leaders in Swiss ski resort Davos.
Oxfam said urgent action was needed to tackle the "inequality crisis" and called on world leaders to take action to crack down on tax-dodging by the rich, which denies governments in the developing world billions of pounds a year which could be used on health, education and anti-poverty measures.
The report found that the gap between rich and poor had widened "dramatically" over the past 12 months.
As recently as 2010, the combined wealth of the 388 richest people was needed to equal that of the poorest half of the world, but that number has since plummeted to 80 last year and 62 now.
The total wealth of the poorest half of the world fell by a trillion US dollars since 2010 even though the actual number of people in this group rose by 400 million, said the report.
Meanwhile, the wealth of the super-rich 62 rose by more than half a trillion dollars over the same period to $1.76 trillion. This equates to an average of around $20bn for each of the 62, who include just nine women.
Although the number of people living in extreme poverty halved between 1990 and 2010 globally, the average annual income of the poorest 10% has increased by less than $3 a year over the past 25 years.
Oxfam said action on tax should form part of a three-pronged approach, alongside increased investment in public services and action to boost the income of the lowest paid, with priority given to ending the era of tax havens.
Allowing governments to collect tax owed is "vital" to meeting the new international development goal of eliminating extreme poverty by 2030, the charity said.
Oxfam GB chief executive Mark Goldring said: "It is simply unacceptable that the poorest half of the world population owns no more than a small group of the global super-rich - so few, you could fit them all on a single coach.
"World leaders' concern about the escalating inequality crisis has so far not translated into concrete action to ensure that those at the bottom get their fair share of economic growth. In a world where one in nine people go to bed hungry every night we cannot afford to carry on giving the richest an ever bigger slice of the cake.
Globally, the super-rich are estimated to have a total of $7.6trn stashed in offshore accounts, depriving governments around the world of $190bn in tax revenues each year, said the report.
As much as 30% of all African financial wealth is believed to be held offshore, costing $14bn in lost tax revenue each year - enough to save four million children's lives a year through improved healthcare and employ enough teachers to get every African child into school - said Oxfam.
Nine out of ten WEF corporate partners have a presence in at least one tax haven and it is estimated that tax dodging by multinational corporations costs developing countries at least $100bn a year, said Oxfam.
Corporate investment in tax havens increased almost quadrupled between 2000 and 2014.
Mr Goldring said: "Ending extreme poverty requires world leaders to tackle the growing gap between the richest and the rest which has trapped hundreds of millions of people in a life of poverty, hunger and sickness.
"It is no longer good enough for the richest to pretend that their wealth benefits the rest of us when the facts show that the recent explosion in the wealth of the super-rich has come at the expense of the poorest."