Rather than being concerned that ProPublica published that Jeff Bezos, Elon Musk and Warren Buffett paid no tax in some years, the US government is investigating how that information leaked to the press.

ProPublica alleges Amazon's Bezos paid no tax in 2007 and 2011, while Tesla's Musk paid nothing in 2018.

A White House spokeswoman called the leak "illegal", and the FBI and tax authorities are investigating.

ProPublica said it was analysing what it called a "vast trove of Internal Revenue Service data" on the taxes of the billionaires, and would release further details over coming weeks.

While the BBC has not been able to confirm the claims, the alleged leak comes at a time of growing debate about the amount of tax paid by the wealthy and widening inequality.

ProPublica said the richest 25 Americans pay less in tax - an average of 15.8 percent of adjusted gross income - than most mainstream US workers.

Jesse Eisinger, senior reporter and editor at ProPublica, told the Today Programme: "We were pretty astonished that you could get it [tax] down to zero if you were a multi-billionaire. Actually paying zero in tax really floored us. Ultra-wealthy people can sidestep the system in an entirely legal way."

The website said that "using perfectly legal tax strategies, many of the uber-rich are able to shrink their federal tax bills to nothing or close to it" even as their wealth soared over the past few years.

The wealthy, as with many ordinary citizens, can reduce their income tax bills via such things as charitable donations and drawing money from investment income rather than wage income.

ProPublica, using data collected by Forbes magazine, said the wealth of the 25 richest Americans collectively jumped by $401 billion from 2014 to 2018 - but they paid $13.6 billion in income tax over those years.
According to reports in the US, Michael Bloomberg, a former mayor of New York whose tax details were among the documents, said the disclosure raised privacy concerns and he would use "legal means" to uncover the source of the leak.