British troops will be spearhead a 10,000-strong European Union force sent to Africa on peacekeeping missions.

Speaking in Ethiopia on Thursday, Tony Blair said that they will serve as members of "rapidly-deployable battle groups" available for action in Africa by 2006.

In a speech about the problems facing Africa, the prime minister promised the continent a "real commitment" to change.

The Conservatives, however, attacked the plan. Nicholas Soames, the shadow defence secretary, said it was "a task too far".

Meanwhile the chancellor has clashed with the European commission after he suggested too much of the EU's aid budget is being spent on relatively rich regions such as the Balkans rather than Africa.

Chris Patten, European commissioner for external relations, hit back saying: "Mr Brown is not the first British minister to fail to compare like with like in taking an opportunistic swipe at the spending of EU aid in third world countries.

"The commission's record in providing development assistance to alleviate poverty in the poorest countries in the world compares well with other European and international donors."