The chancellor believes international aid should be doubled

Mr Brown's trip is designed to highlight how the UK wants to make Africa's problems a priority of its chairmanship of the G8 this year.

He will see an HIV/Aids orphanage in Tanzania and a women's credit union in Mozambique before chairing a meeting of the Commission for Africa in Cape Town.

At slums in Nairobi on Wednesday, he said education needs had to be tackled.

Slum visit

Speaking outside the Olympic Primary School, Mr Brown said: "It is simply not acceptable in the modern age for the rest of the world to stand by and have hundreds of millions of children not getting the chance at education."

He pointed to international plans to invest $10bn for education in Africa over the next decade.

The school is on the edge of Kibera, where 800,000 live, often in huts made of mud, scrap metal and cardboard.

Mr Brown's aides say he wants to find out more about the Kenyan Government's education policies, which included introducing free primary education in early 2003.

The chancellor has already unveiled proposals for a G8 aid package which he has likened to the Marshall Plan used by the United States to rebuild Europe after World War Two.

Responding to the trip, Conservative shadow foreign secretary Michael Ancram said: "I was amazed to see that given his declared intentions to save Africa from poverty and oppression Gordon Brown's atlas, like Tony Blair's, seems to have a gaping hole in that continent where mine shows Zimbabwe."