Growing inequality means a group of men that could easily fit into one golf buggy own the same wealth as half the world, campaigners have warned world leaders gathering for talks in Switzerland.
The eight billionaires have riches equivalent to the wealth of the world's 3.6 billion poorest people, according to research by Oxfam.
It said the gap between rich and poor was far greater than had been feared and called for an overhaul of a "warped" economy that allowed a small group to have more wealth than they could ever spend while one in nine people went hungry.
Theresa May and Philip Hammond will attend the World Economic Forum of global political and business leaders in Davos this week.
The annual event, held in a luxury Swiss ski resort, is often criticised for being little more than a talking shop for the rich and powerful.
Oxfam is calling on international leaders to improve international cooperation to stop tax dodging, action to encourage companies to act for the benefit of staff as well as shareholders, wealth taxes to fund healthcare, education and job creation, and improvements in opportunities for women.
It also urged business chiefs to commit to paying a living wage and their fair share of tax.
Mark Goldring, Oxfam GB chief executive, said: "This year's snapshot of inequality is clearer, more accurate and more shocking than ever before.
"It is beyond grotesque that a group of men who could easily fit in a single golf buggy own more than the poorest half of humanity.
"While one in nine people on the planet will go to bed hungry tonight a small handful of billionaires have so much wealth they would need several lifetimes to spend it.
"The fact that a super-rich elite are able to prosper at the expense of the rest of us at home and overseas shows how warped our economy has become.
"Inequality is not only keeping millions of people trapped in poverty, it is fracturing our societies and poisoning our politics.
"It's just not right that top executives take home massive bonuses while workers' wages are stagnating or that multinationals and millionaires dodge taxes while public services are being cut."
Oxfam said out-of-control pay ratios meant the average pay of FTSE100 chief executives was 129 times that of the average employee and works out to the equivalent of 10,000 people working in Bangladeshi garment factories.
It said new and better data on the distribution of global wealth, particularly in India and China, showed the poorest had less wealth than previously thought.
The charity said if the information had been available when it carried out research last year, its report would have found that nine billionaires owned the same wealth as the poorest half of the planet instead of 62.
Among the eight billionaires from the latest research, Bill Gates, who tops the list, and Warren Buffett, the world's third richest man, are known philanthropists who have pledged to give away most of their wealth.
Oxfam said the move was "welcome" but did not replace the needed for a fair tax system.
Its report added: "The fortune of Bill Gates has risen 50% or 25 billion US dollars since he left Microsoft in 2006, despite his commendable efforts to give much of it away.
"If billionaires continue to secure these returns, we could see the world"s first trillionaire in 25 years.
"In such an environment, if you are already rich you have to try hard not to keep getting a lot richer."
Oxfam said under its calculations, which were based on the Forbes billionaires list and Credit Suisse global wealth distribution data, just under 10% of the world's poorest were in debt.
That included a "tiny fraction" of workers who may be earning good salaries but were paying off debts such as student loans or were in negative equity.
The number of billionaires who owned the same as half the world went up to 56 if everyone in net debt was taken out of the calculation.
But the charity said that most in the bottom half of the world's population were very poor and faced a daily struggle to survive.
Mr Goldring said: "Extreme inequality isn't inevitable - with the right policies, world leaders can rebalance our broken economies so they work for all of us and bring the end of poverty closer.
"We need a new common sense approach that ensures a fair deal for workers and producers; requires those who can afford it to pay their fair share of tax; and ensures that women get a fair chance to realise their potential.
"Oxfam welcomes the Prime Minister's pledge to tackle inequality in the UK - we'd like to see her make a similar commitment on the global stage.
"Standing up to powerful interests and corporate bad behaviour won't be easy but is vital if we're to ensure a better future for people at home and around the world."
The Adam Smith Institute free market think tank accused Oxfam of putting out misleading information.
Head of research Ben Southwood said the welfare of world's poor was improving with the proportion of the global population surviving on less than 2 dollars-a-day - falling from 69% in 1981 to 43% in 2008.
"Each year we are misled by Oxfam's wealth statistics. The data is fine - it comes from Credit Suisse - but the interpretation is not," he said.
"It is not the wealth of the world's rich that matters, but the welfare of the world's poor - and this is improving every year.
"The consumption of the world's poor continues to rise, as does their education, healthcare, and height."