Foreign investors have bought up more than 100 million hectares of land in poor countries in the last decade in deals which could be contributing to hunger and poverty, campaigners have warned.
An area the size of London was sold off or leased every six days to outside investors in developing countries between 2000 and 2010, with more than 60% of investments taking place in nations with serious hunger problems, Oxfam said.
But two-thirds of investors planned to export everything they grew on the land, according to a new report - Our Land, Our Lives - from the aid agency.
Oxfam is warning that sales are not adequately regulated or policed to prevent land grabs in which poor people are evicted from their land and homes, leaving them destitute and unable to feed themselves or make a living.
The last global food price crisis in 2008 and 2009 saw land deals treble because they were seen as a profitable investment, Oxfam said, and with food prices at around record levels once more, there could be another wave of land grabs.
The aid agency is also raising concerns about the amount of land which could be given over to growing crops for biofuels, a renewable energy source which can divert land away from growing food.
Oxfam is calling on the World Bank - a major investor - to freeze its agricultural investments, sending a strong signal to other investors to stop land grabs and improve protections of local people in sales.
Chief executive Barbara Stocking said: "The rush for land is out of control and some of the world's poorest people are suffering hunger, violence and greater poverty as a result. The World Bank is in a unique position to help stop land grabs becoming one of the biggest scandals of the century and must act now."
She also called on the UK Government to put food and hunger at the heart of the agenda when it has the presidency of the G8 next year.