A "progressive wealth tax" would be the ideal solution to resolving global wealth inequality, according to French economist Thomas Piketty, associate chair at the Paris School of Economics and author of 'Capital in the Twenty-First Century'.

Mr Piketty said this would require better information on wealth. “This is where international co-operation can play a role,” he said.

The French economist compiled data on wealth from Forbes magazine, which carries wealth rankings each year. This shows that the top 1 per cent of wealth holders saw their incomes grow by an average of 6.8 per cent a year between 1987 and 2013, including the rate of inflation.

This was more than three times the average wealth per adult and just more than twice the growth in world GDP.

Mr Piketty is "less pessimistic" than most commentators about the possibility of a progressive wealth tax regime being introduced. "The whole history of tax is full of surprises," he said, noting that the highest rate of income tax in Germany and Japan was 90 per cent between 1945 and 1948 when the United States ran their economies post the Second World War.

“The issue of inequality did not start 10 years ago...its important to address that in the future and be a bit more informed,” he said.

Mr Piketty was speaking at the Tasc annual conference in Croke Park today, which drew a capacity crowd of 650.