A leaked World Bank report into investors from rich nations buying up African farmland has intensified campaigners' fears that the growing trend is marginalising local producers.

After a spate of investments in African land by sovereign wealth funds looking for gains on rising commodity prices and by countries such as China worried about their own food security, the World Bank launched research into the area. Its report is due to be published next month, but a draft copy leaked to the Financial Times painted a picture of largely speculative investment badly lacking agricultural expertise, and a rush towards countries with lax laws. It mentioned only a handful of successes.

"Investor interest is focused on countries with weak land governance," the draft said. Although investment deals promised jobs and infrastructure "investors failed to follow through on their investment plans, in some cases after inflicting serious damage on the local resource base". The report also flagged that "the level of formal payments required was low", thereby fuelling speculative investment.

As commodity prices have soared on the back of rising global food demand, weather fluctuations and a growing biofuels industry, anti-poverty campaigners have grown increasingly concerned about speculative land-grabbing in Africa and other developing regions.

They argue that investors crowd out the poorest local producers and at the same time invest little in improving the agricultural processes needed to meet the huge jump in world food production required to feed a burgeoning population.

Aurelie Walker, Fairtrade Foundation's trade policy advisor, said: "With the policy frameworks in place, investment in land for agriculture can potentially act as a catalyst for development. But this is rarely the case. Governments with weak institutions laws and regulations are easy targets for wealthy investors."

The UN Food and Agriculture Organisation, the UN Conference on Trade and Development (Unctad) and the World Bank have been discussing a code of conduct for land buyers in Africa and this latest research on patterns so far is likely to feed into that.

A spokesman for the World Bank confirmed the report The Global Land Rush: Can it yield sustainable and equitable benefits? would be released in August but said that it was still being revised. "The World Bank undertook research on farmland acquisitions at the request of developing countries, and to help ensure that their citizens, including the poor and farmers, benefit from foreign investments in this area," he added.While campaigners will likely welcome the wide-ranging report as a base for creating more enforceable guidelines, some bodies argue there will still be big questions over implementing new rules. The United Nations, for example, believes African governments themselves must be more demanding in their trade relationships with other countries, something that the Fairtrade Foundation echoes.

"It's also the responsibility of governments in poor countries to consult with local communities and ensure land sales are in the best interest of their people and not an opportunity to make a fast buck," said Walker.