“The global economy is broken,” Oxfam says in a new report which finds eight billionaires own as much wealth as the poorest half of the world’s population.

The charity has urged the all-male group to “play their part” in bridging a gap it describes as “obscene.”

Among other things, Oxfam calls for a crackdown on tax dodging, a living wage for all employees, and asks the rich not to use their economic wealth in return for political favours.

“We’ve seen countries in the last ten years that have bucked the trend and that are going in the other direction, and are reducing the gap between rich and poor. One thing they do is they get the rich to pay their tax. We’ve got a situation where billionaires are paying (proportionally) less tax often than their cleaner or their secretary. That’s crazy. We’re seeing wealth channelled upwards,” said Oxfam Policy Advisor, Max Lawson.

The wealth of the super rich has reportedly surged by around 11 percent per year since 2009 while new data from India and China have indicated that the poorest half of humanity own even less than previously estimated.

The Oxfam report is not without its critics who say that the figures are reliable but the analysis of them is not.

The head of research at the Adam Smith Institute, Ben Southwood, said the wealth of the world’s rich does not matter compared to the welfare of the world’s poor, which is improving year on year.

He added: “Each year we are misled by Oxfam’s wealth statistics. The data is fine – it comes from Credit Suisse – but the interpretation is not.”

Mark Littlewood, of the Institute of Economic Affairs, said Oxfam should focus on ways to boost growth, he said: “As an “anti-poverty“charity, Oxfam seems to be strangely preoccupied with the rich”.

Several billionaires have already said that they will donate vast sums of money to charitable causes. Facebook founder Mark Zuckerberg and his wife Priscilla Chan have pledged to give away 99% of their wealth within their lifetime. That equates to approximately 42 billion euros.

This month former American billionaire Chuck Feeney signed over his last philanthropic check, having donated almost his entire fortune.

Although some billionaires choose to donate substantial amounts of money in this way, Max Lawson says this does not resolve the fundamental problem of wealth inequality.

“If billionaires choose to give their money away then that is a good thing. But inequality matters and you cannot have a system where billionaires are systematically paying lower rates of tax than their secretary or cleaner,” Lawson added.

The world’s eight richest billionaires

1. Bill Gates (US): co-founder of Microsoft (net worth $75bn)

2. Amancio Ortega (Spain): founder of Zara owner Inditex (net worth $67bn)

3. Warren Buffett (US): largest shareholder in Berkshire Hathaway (net worth $60.8bn)

4. Carlos Slim Helu (Mexico): owner of Grupo Carso (net worth $50bn)

5. Jeff Bezos (US): founder and chief executive of Amazon (net worth $45.2bn)

6. Mark Zuckerberg (US): co-founder and chief executive of Facebook (net worth $44.6bn)

7. Larry Ellison (US): co-founder and chief executive of Oracle (net worth $43.6bn)

8. Michael Bloomberg (US): owner of Bloomberg LP (net worth $40bn)

Source: Forbes billionaires’ list, March 2016

The report comes as influential figures and many of the world’s wealthiest gather in Davos, Switzerland, for this year’s World Economic Forum.