Senator Bernie Sanders speaks to a reporter outside of the Capitol, September 28, 2021. (Getty images)

US Senator Bernie Sanders has denounced the rigged economic and political system in America, which has allowed billionaires to become significantly richer during the pandemic while others are struggling with financial hardship.

A new report from the Institute for Policy Studies, Patriotic Millionaires, Fight Inequality Alliance, and Oxfam has found that America�s wealthiest individuals have seen their ranks grow in the past five years, with US billionaires becoming $2 trillion richer during the pandemic alone.

Globally there are 2,660 billionaires, according to the Oxfam report. As of November 30, 2021, those billionaires held a combined wealth of $13.76 trillion. The US alone accounts for 740 of those billionaires, holding $5.1 trillion collectively.

Sanders, an Independent from Vermont and former presidential candidate, attributed the widening wealth gap in the US to a corrupt system, where elected officials reward billionaires with tax breaks and other incentives in return for their campaign contributions.

A rigged economic and political system is when billionaires spend $1.2 billion in campaign contributions to buy politicians in the last election, become $2 trillion richer during the pandemic and pay a lower effective tax rate than a nurse, Sanders wrote in a tweet on Friday.

Yes, we must abolish Citizens United, he added, referring to a controversial January 21, 2010 decision by the Supreme Court that reversed century-old campaign finance restrictions.

The court ruled that corporations, unions, and wealthy donors have a free speech right to spend unlimited funds to influence American elections.

Citizens United has paved the way for an unrepresentative elite donor class to disproportionately source election spending in the country.

Campaign contributions have seen a steep rise since then, with nearly half of the so-called super PAC money coming from just 25 billionaires over the past decade.

Before Citizens United, the high court had upheld certain spending restrictions, arguing that the government had a role in preventing corruption.

Critics charge that elected officials often feel duty-bound to return the favor once they assume office.

The Oxfam report said that a wealth tax of 2 percent on individuals holding over $5 million, 3 percent for those with over $50 million, and 5 percent for those with over $1 billion would bring in $928.39 billion annually.

That amount is enough to cover the largest and most prominent parts of US federal spending.