Tony Blair says Britain will do all it can to avert a "catastrophic" famine in southern Africa.

The prime minister was speaking as it was revealed more than 14 million people - half of them children - are facing starvation.

Aid agencies say this is the worst food crisis in the region for a decade.

The UK is backing an international charity appeal, launched by the Disasters Emergency Committee (DEC) on Thursday, to provide food, medical and agricultural assistance.

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Those at risk - in Zimbabwe, Angola, Zambia, Malawi, Mozambique, Swaziland and Lesotho - have suffered at the hands of drought, flooding and political instability.

Mr Blair said: "It is a genuine tragedy that this natural disaster has been visited upon the people of southern Africa.

"The consequences are potentially very serious and we have ordered action at every level we can."

He said the government was making aid available and was working with other aid and development organisations to "get as much aid to the area as possible".

	:	Southern Africa famine
In pictures: Southern Africa famine

"This is a very serious situation, it is truly a tragedy at a time when there is some signs of hope in Africa," Mr Blair added.

The British public is being asked to help with the launch on Thursday of an appeal by the DEC, which aims to provide food, medical and agricultural assistance.

DEC unites 13 leading British aid agencies such as the British Red Cross, Oxfam, Save the Children, CAFOD and Christian Aid to co-ordinate and maximise income from the public at times of major disaster overseas.

Famine victims are eating maze shoots before they grow

Speaking at the appeal launch, Judith Melby, emergencies officer for Christian Aid, said she had just returned from Angola where an estimated four million people had been displaced after 27 years of civil war.

"We figure that there are a million people who are totally dependent on food assistance at the moment and the food assistance is not there," she said.

"If they don't get it before March next year we will have a million and a half people."

The World Food Programme originally launched an appeal at the beginning of July to raise $500m for the southern African countries but has only received 22% of the funding they need from foreign governments.

Britain, Canada, Denmark, Ireland, New Zealand, Spain, the Netherlands and the United States have responded to the WFP call. The Church of the Latter Day Saints, also known as the Mormons, has donated $1 million.

Oxfam said other governments must do more and follow Britain's example.

"We have people out in southern Malawi and while it's a poor area anyway, things are getting distinctly worse. It's now critical.

Lewis Sida, of Save the Children UK, said: "We are all responding to this and are asking the public to please give money to us collectively and collectively we will do what we can to address this."

A spokeswoman for DEC said the appeal was being launched due to the sheer scale of the crisis.

She said: "A lot of agencies have been working very hard for a long time trying to alert the world to this latest plight.

"It's also about prevention. We don't want this to get any worse. No one wants to wait until we see those awful pictures on our television screens.

"The harvest is poor. Many have been eating maize shoots before they even grow because they are so hungry."