The study estimating that the extent of global private financial wealth held in offshore accounts — excluding non-financial assets such as real estate, gold, yachts, and racehorses — puts the sum at somewhere between $21tn and $32tn.
The estimate is almost three times the previous estimate of $11.5tn in 2005.
Fewer than 100,000 people own $9.8tn of offshore assets, according to the research.
The research was carried out for pressure group Tax Justice Network, which campaigns against tax havens, by James Henry, the former chief economist at consultants McKinsey & Co.
Mr Henry used data from the World Bank, IMF, UN, and central banks.
The report also highlights the impact on the balance sheets of 139 developing countries of money being held in tax havens by private elites, putting wealth beyond the reach of local tax authorities.
The research estimates that, since the 1970s, the richest citizens of these 139 countries had amassed $7.3tn to $9.3tn of “unrecorded offshore wealth” by 2010.
Private wealth held offshore represents “a huge black hole in the world economy”, according to Mr Henry.
“These estimates reveal a staggering failure: Inequality is much, much worse than official statistics show, but politicians are still relying on trickle-down to transfer wealth to poorer people,” said John Christensen of the Tax Justice Network.
“People on the street have no illusions about how unfair the situation has become.”
Mr Henry said that private banks — which are desperate to woo the super-rich — are helping the global elite to keep hold of their huge assets.
He said: “[Their wealth is] protected by a highly-paid, industrious bevy of professional enablers in the private banking, legal, accounting, and investment industries taking advantage of the increasingly borderless, frictionless global economy.”
According to the Tax Justice Network, the consequences of this tax avoidance are severe.
“Secrecy distorts trade and investment flows, and creates a criminogenic environment for a litany of evils that hurt the citizens of rich and poor countries alike,” the tax network said.
“It’s not just developing countries that suffer: European countries like Greece, Italy, and Portugal have been brought to their knees by decades of secrecy and tax evasion.”
Estimates suggest that if the interest on the huge sums being lost were taxed at a rate of around 30%, some €121bn would be generated for the treasuries around the world.