Eight billionaires have riches equivalent to the same wealth as half the world, campaigners have warned world leaders gathering for talks in Switzerland.

The research by Oxfam found that 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.