New Delhi, Jan. 21 -- Nearly 400 millionaires and billionaires from 24 countries have urged world leaders to impose higher taxes on the ultra-wealthy, warning that extreme concentrations of wealth are distorting democracy, deepening inequality and accelerating global instability.

An open letter released to coincide with the World Economic Forum in Davos calls on political leaders to act decisively to close what it describes as the widening gulf between the super-rich and the rest of society.

The signatories - almost 400 wealthy individuals from across Europe, the Americas, Asia and Africa - argue that extreme wealth is now reshaping political systems and public life.

The letter, signed by figures including Mark Ruffalo, Brian Eno and A...