More than 200 millionaires are calling on the elite attending the World Economic Forum in Davos this week to address the problem of excessive wealth and tax the super-rich to help reduce the burden on ordinary households, CNBC reports.

The millionaires, who call themselves a group of wealthy Americans who share a deep concern about America's destabilizing levels of inequality, called for similar measures in their campaign last year.

The message warns of an era of extremes marked by rising poverty, property inequality, anti-democratic nationalism, depressed environmental conditions, and declining opportunities for the average worker to earn a living.

The letter questions the mission of the World Economic Forum in the absence of concrete action.

The campaign has 206 participants from 12 countries, including Abigail Disney, heiress to the multimedia entertainment empire, and actor Mark Ruffalo.