Davos, Switzerland - The world's wealthiest five men have more than doubled their fortune since 2020, the charity Oxfam said on Monday, as it called on nations to resist the ultra-rich's influence over tax policy.

A report from the charity, published as the global elite hobnob at the World Economic Forum in Davos this week, said their wealth rose from $405 billion in 2020 to $869 billion last year.

Yet since 2020, nearly 5 billion people worldwide have grown poorer, Oxfam said.

Billionaires are today $3.3 billion richer than they were in 2020, despite many crises devastating the world's economy since this decade began, including the Covid pandemic.

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Oxfam's yearly report on inequality worldwide is traditionally released just before the forum opens on Monday in the Swiss Alpine resort.

The charity raised concerns over increasing global inequality, with the richest individuals and companies amassing greater wealth thanks to surging stock prices, but also significantly more power.

"Corporate power is used to drive inequality: by squeezing workers and enriching wealthy shareholders, dodging taxes, and privatising the state," Oxfam said.

The charity also accused corporations of driving "inequality by undertaking a sustained and highly effective war on taxation," with far-reaching consequences.

Oxfam said states handed power over to monopolies, allowing corporations to influence the wages people are paid, food prices, and which medicines individuals can access.

"Around the world, members of the private sector have relentlessly pushed for lower rates, more loopholes, less transparency, and other measures aimed at enabling companies to contribute as little as possible to public coffers," Oxfam added.

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The charity said thanks to intensive lobbying over tax policymaking, corporations have been able to pay lower corporate taxes, thereby depriving governments of money that could be used to financially support the poorest in society.

Corporate taxes have significantly dropped in OECD countries from 48% in 1980 to 23.1% in 2022, Oxfam noted.

To address the imbalance, Oxfam called for a wealth tax on the world's millionaires and billionaires that it says could bring in $1.8 trillion dollars each year.

The charity also called to cap CEO pay and break up private monopolies.