A best-selling book by a French economist on rising wealth inequality has come under fire after the Financial Times newspaper said that an investigation it carried out found a series of errors that skewed the author's findings.
The FT said it found mistakes and unexplained entries in the spreadsheets underpinning Thomas Piketty's Capital in the Twenty-First Century.
The roughly 700-page book was published this year and gained quick popularity, hitting the top of the New York Times bestseller list in May.
Piketty has been travelling the world promoting his book, meeting with top officials such as US Treasury Secretary Jacob Lew, and earning the praise of decorated economists.
Piketty's work shows that wealth inequalities are heading back up to levels last seen before World War One. The FT said its investigation undercuts this claim and indicates there is little evidence in Piketty's original sources to bear out the thesis that an increasing share of total wealth is held by the richest few.
In response, Piketty told the FT: "I have no doubt that my historical data series can be improved and will be improved in the future ... but I would be very surprised if any of the substantive conclusion about the long-run evolution of wealth distributions was much affected by these improvements."
The newspaper's finding comes a little more than a year after another well-known economic research study came under attack for errors, which the authors later accepted responsibility for.
That controversy involved a 2010 study by Harvard economists Kenneth Rogoff and Carmen Reinhart, key parts of which were undone by a 28-year-old graduate student.
Piketty did not immediately reply to an email from Reuters seeking comment.