Foreign investment in arable land in Mali increased by 60% between 2009 and 2010, says a report published on Thursday to coincide with the first international farmers' conference to tackle the global rush for land.

The report, by the US-based Oakland Institute and the Malian national farmers organisation, estimates that more than 544,500 hectares of Malian land have been leased or were under negotiation for lease by the end of 2010. The bulk of these land deals – covering an area the report says could sustain more than half a million small farmers – were negotiated by just 22 foreign agri-investors. Less than 5% of west Africa's largest country is arable.

Mali has been at the centre of agri-investor interest and farmer resistance to the largescale deals that have sparked growing concern from international aid and development organisations.

"Corporations, fund managers and nations anxious to secure their own future food security have sought and secured large landholdings for offshore farms or speculation," says the report, noting that the food and fuel crises of 2008 appear to have jump-started the rush to acquire farmland across Africa. The report updates a study produced by the Oakland Institute earlier this year, which showed Harvard and other major American universities were key emerging investors in the continent's farmland.

Thursday's report notes that 40% of the recent large land deals negotiated in Mali have been flagged for the production of agrofuels, despite government assurances that such investments were to strengthen food security and transform the country into a major food supplier for the region.

An "ideological divide" has blocked progress on negotiating investments that benefit local communities, says the report. "While [industrialised agriculture] may involve smallholder support projects, the purpose is rarely to strengthen and promote traditional farming systems … Rather the aim is to 'modernise' them, increase competitiveness, focus on value chains for commodities, and orient smallholders towards the global marketplace."

The report levels significant blame on the World Bank, which it says has "shaped the economic, fiscal and legal environment of Mali in a way that favours the acquisition of vast tracks of fertile lands by few private interests instead of bringing solutions to the widespread poverty and hunger plaguing the country". Mali ranked 175 out of 187 countries in this year's UN Human Development Index. The most recent figures suggest more than 50% of the population live on less than $1.25 a day and nearly a third of children under the age of five are malnourished.

The famine and food crisis in the Horn of Africa has pushed policymakers to focus on the potential of Africa's small farmers to strengthen countries' food security and ultimately drive economic development on the continent. Smallscale farmers are credited with producing as much as 80% of Africa's food.

Much of Mali's large deals concern state-owned land, where the informal rights of communities living on the land are not protected by law, and rarely recognised by public officials.

Ibrahima Coulibaly, head of the Malian national farmers' organisation, said "land-grabbing is a denial of historical rights", and that in many cases farmers have for generations lived on land that only formally became state assets after independence in the 1960s.

Publication of the report comes as hundreds of smallholder farmers and civil society activists from 30 countries descend on Selingue, in southern Mali, to draft a strategy to strengthen local communities' resistance to "land grabbing".

The conference, which runs from Thursday to Sunday, and is co-ordinated by the Malian national farmers organisation and the international peasants' movement La Via Campesina, plans to focus on examples of farmers' resistance to land grabs. While large land deals have received increasing attention from international organisations, conference organisers argue this has often been directed by large NGOs and rarely by small farmers themselves.

Research by Oxfam, published this year, suggests that nearly 230m hectares of land – an area the size of north-west Europe – have been bought or leased, largely in Africa, mostly by foreign companies, in thousands of secretive deals made since 2001. Earlier, the World Bank had published estimates putting that figure at just under 60m hectares.