Only three of the treasures looted from the Maqdala fortress have been returned

The treasures were looted from the palace of an Ethiopian emperor, after his defeat by a British force in 1868.

A letter was handed to one of Mr Blair's aides while he was in the Ethiopian capital, Addis Ababa for a meeting of his Commission for Africa.

The treasures, which include a gold crown, are worth $3bn, campaigners say.

But the most valuable item is one of two copies of the Kebra Negast - or Glory of Kings - Ethiopia's holy book which is held in the British Library in London.

'Immeasurable value'

"If they're championing the preservation of African culture and heritage, nothing could more effectively demonstrate that," Andreas Eshete of the Addis Ababa University told the BBC's Network Africa programme.

Mr Blair (r) has pledged to help raise African living standards

The Commission for Africa was set up by Mr Blair in order to help reduce poverty in the world's poorest continent.

"These things were forcibly taken from Ethiopia and have very little value and limited access in Britain but have immeasurable value and unlimited access in Ethiopia," said Mr Andreas, president of the Association for the Return of The Maqdala Ethiopian Treasures (Afromet).

The forces of Emperor Tewodros II were defeated at the Battle of Maqdala.

Almost 500 manuscripts were carried away on 200 mules and 15 elephants by British soldiers, said UK historian Richard Pankhurst.

They are now held in museums across the UK, as well as in some private collections, including that of the British royal family.