Josette Sheeran from the UN World Food Programme has spoken about the shortages.
The head of the UN World Food Programme has said urgent action is required to stimulate food production and help the poor cope with soaring food prices.
Josette Sheeran told the BBC that an additional 100 million people, who did not need assistance six months ago, could not now afford to purchase food.
Her warning came ahead of a meeting in London to discuss the rise in prices and an EU policy encouraging biofuels.
Biofuels are intended to tackle climate change but can take away farm land.
Earlier, Latin American leaders had warned about the growth in production of biofuels, which are derived from plant crops.
In an interview with the BBC, Ms Sheeran said she would be stressing the urgent need to tackle the global rise in food and commodity prices when she attended the meeting hosted by UK Prime Minister Gordon Brown on Tuesday afternoon.
The high food prices are hitting more than 100 million individuals around the world who can no longer afford to purchase the food
Josette Sheeran, World Food Programme
"We find that people are being thrown into the urgent category and we really want to make the point that the clock is ticking and we need to help people now meet their nutritional needs," she said.
"We're seeing about 100 million people... who maybe didn't need assistance six months ago but today simply can't afford enough food for their family."
Ms Sheeran said the price of rice in Asia had soared from $460 a ton on 3 March to more than $1,000 seven weeks later. The global prices of wheat, rice and maize have nearly doubled in the past year.
Ms Sheeran said the crisis required large-scale, high-level action by the international community, focused on both emergency and longer-term solutions.
Crops used for biofuels can take away land that was used to produce food
In the short term, she said the WFP needed increased donations to make sure it could meet the needs of those who already relied on it, because its budget requirements were rising by several millions of dollars a week in line with the cost of food.
"We can purchase less food than we could in June - in fact, 40% less," she said.
Ms Sheeran said the international community needed to pay attention to the food supply system and look at all the factors that have increased demand.
"Certainly, biofuel is one of those things that is impacting it and we need the experts to sit down and look at how much food is needed and to make sure people can get it at an affordable price," she said.
Latin American concern
Writing ahead of Tuesday's meeting, Mr Brown said rising food prices posed as great a threat to world prosperity as the global credit crisis and warned that they threatened to reverse progress made to alleviate poverty in the developing world.
We need to look closely at the impact on food prices and the environment of different production methods and to ensure we are more selective in our support
"Tackling hunger is a moral challenge to each of us and it is also a threat to the political and economic stability of nations," he said in a statement.
Food riots earlier this month in Haiti, which is highly reliant on imports of food and fuel, led to the deaths of at least six people, including a UN peacekeeper.
There has also been unrest in Burkina Faso, Cameroon, Egypt, Indonesia, Ivory Coast, Mauritania, Mozambique and Senegal.
Mr Brown said he feared the use of agricultural land to produce biofuels, which he said were known to be "frequently energy-inefficient", might have been a factor in driving up food prices.
South Americans warn over biofuels
"We need to look closely at the impact on food prices and the environment of different production methods and to ensure we are more selective in our support," he added.
"If our UK review shows that we need to change our approach, we will also push for change in EU biofuels targets."
The EU has come under criticism for its target of getting 10% of road transport fuel from crops by 2020, while ethanol production is on course to account for some 30% of the US maize crop by 2010.
Biofuels are being developed in many countries as an alternative to fossil fuels, on the basis that they absorb carbon dioxide while growing and therefore contribute less to climate change.
But there are concerns that forests, which also absorb large amounts of carbon, are being cleared to make way for biofuel crop plantations, as well as that their cultivation is taking land out of food production.
Speaking at the UN in New York, Bolivian President Evo Morales attacked those who put luxury cars ahead of human lives. His Peruvian counterpart, Alan Garcia, said using land for biofuels was putting food out of reach for poor people.
The comments came after one of the world's major producers, Brazil, announced a venture in Ghana to grow sugar cane for bio-ethanol.
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