Just 62 people own as much as the poorest half of the world's population put together, according to a report by Oxfam.
The finding has sparked calls for urgent action to tackle the mounting "inequality crisis".
The aid charity said in 2010 the total wealth of the 388 richest people was needed to equal the poorest half of the world, but that number fell to 80 last year and stands at 62 now.
The Oxfam report, published ahead of the World Economic Forum in the Swiss ski resort of Davos, also said the wealth of the richest 1% - around 73 million out of the world's 7.3 billion people - was now as much as everyone else on the planet combined.
World leaders, including David Cameron, are being urged by Oxfam to clampdown on tax-dodging by the rich, which it said was depriving poorer countries of cash that could be spent on education, health, and measures to combat poverty.
The report said the super-rich are estimated to have a total of $7.6 trillion in offshore accounts, which means governments globally are missing out on tax revenues of $190 billion each year.
For developing countries, tax dodging by multinational corporations cost them at least $100 billion a year, said Oxfam.
The report said since 2010, the total wealth of the poorest half of the world had fallen by a trillion US dollars even though the number of people in this group had risen by 400 million.
At the same time, the wealth of the 62 super-rich rose by more than half a trillion dollars over the same period to 1.76 trillion. This equates to an average wealth of $40.6 billion per member of this exclusive club.
Meanwhile the average wealth of the bottom half of the world's population is a mere $699 per person.
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.
"Tackling the veil of secrecy surrounding the UK's network of tax havens would be a big step towards ending extreme inequality. Three years after he made his promise to make tax dodgers 'wake up and smell the coffee', it is time for David Cameron to deliver."