The government has promised an extra £3m in new funding to help meet growing food shortages in Afghanistan.
The food aid will be targeted at the most vulnerable people.
The money will be given to a joint United Nations and Afghan government appeal for £40m in food aid.
It will be used to alleviate malnutrition, particularly among pregnant and breastfeeding women.
The International Development Secretary Douglas Alexander said the cash would provide a "safety net" that would will help avoid a humanitarian crisis.
Providing an immediate safety net will help avoid a humanitarian crisis and end the immediate suffering
Douglas Alexander, International Development Secretary
UN research suggests that poor Afghans are struggling to buy food because of rising wheat prices. In Kabul it is estimated that people spend up to 60% of their income on bread alone.
Rising global prices
The UK government says the shortages have been caused by rising global prices made worse by severe cold weather.
Mr Alexander said: "Afghanistan is one of the poorest countries in the world, and least able to cope with spiralling food prices combined with severe winter weather.
"Providing an immediate safety net will help avoid a humanitarian crisis and end the immediate suffering."
He said that the food shortage is evidence of the impact of rising global food prices hitting the poor hardest.
The £3m pledged by Mr Alexander brings the total amount of UK humanitarian aid to Afghanistan to £124m since 2001.
Since 2001 the UK has also spent £490 million on reconstruction and development in the country.
Last December, Prime Minister Gordon Brown announced a further commitment of £450 million to Afghanistan between 2009 and 2012.