UK’s five richest families worth more than poorest 20%

The U.K.'s five richest families own more wealth than the poorest 20 percent of the country, according to research from a leading charity, highlighting the stark inequality that exists in Britain and across the world.

Sports Direct boss Michael Ashley and real estate investor Gerald Grosvenor are among of the five billionaires, who are collectively worth £28.2 billion ($46.9 billion), more than the £28.1 billion wealth of the bottom 12.6 million people in Britain, Oxfam revealed, citing figures from Forbes magazine.

The "deeply worrying" research comes ahead of the U.K.'s budget announcement on Wednesday, with the charity warning that continued austerity measures could thrust 800,000 children and an extra 1.9 million adults into poverty by 2020.

"It's deeply worrying that these extreme levels of wealth inequality exist in Britain today, where just a handful of people have more money than millions struggling to survive on the breadline," Ben Phillips, Oxfam's director of campaigns and policy, said in a press release.

(Read more: Income disparity, fiscal crises threaten 2014: WEF)

Dorling Kindersley | Dorling Kindersley | Getty Images

Incomes of the top 0.1 percent of the population have risen nearly four times faster than for the bottom 90 percent, Oxfam said in the report entitled "A Tale of Two Britains".

The charity raised concerns that government policy is benefiting the rich while disadvantaging the poor. According to the report, 95 percent of the British public have seen a 12 percent real terms drop in disposable income, after housing costs, while the wealthiest 5 percent have seen their disposable income double.

The Treasury told CNBC it appreciated times had been tough for hard working people who are still feeling the effects from the most damaging recession in a century, but said its plan was helping the economy get back on track.

"The government's long term plan is working: delivering the fastest growth of any major European economy, putting more people in work than ever before and cutting the deficit by a third," a spokesperson for the Treasury said in an emailed statement.

"Where possible the government has found the money to help by reducing energy bills, freezing fuel duty, freezing council tax and taking 2.7 million people out of tax by increasing the tax free personal allowance. The biggest risk now to the recovery would be abandoning the plan that's delivering a brighter economic future."

Richest 85 people have more money than bottom 3.5 billion

Oxfam also argues that "extreme inequality" is holding back economic growth and urged the government to tackle tax evasion by the rich, implement a financial transaction tax and raise the minimum wage to a living wage.

The U.K.'s economy has been recovering, growing 1.8 percent in 2013, according the official statistics office, and is expected to continue on a growth path.

"In developed and developing countries alike we are increasingly living in a world where the lowest tax rates, the best health and education and the opportunity to influence are being given not just to the rich but also to their children," the report said.

"While many rich people use a portion of their wealth to support individual good causes, this should not be used as an excuse for governments failing to tackle the problem of growing inequality," Phillips added.

(Read more: Pope attacks mega-salaries and wealth gap in peace message)

Real estate king Gerald Grosvenor and his family, who own over 100,000 acres of land across the globe are top of the list with a net worth of $13 billion, followed by property moguls David and Simon Reuben who are worth $11.5 billion.

London real estate tycoon Charles Cadogan is also one of the top five richest people in Britain with a $6.9 billion worth, along with Sports Direct boss Michael Ashley who is worth $5.5.

This report follows Oxfam research in January ahead of the World Economic Forum in Davos that lifted the lid on the global state of wealth inequality. The richest 85 people in the world own the same amount of wealth equivalent to half the world's population, according to the charity.

—By CNBC's Arjun Kharpal: Follow him on Twitter @ArjunKharpal