Bold investment in poverty relief in Africa is needed to heal the wounds caused by slavery, former United Nations chief Kofi Annan has said.
Former UN chief Kofi Annan wants to see more investment in Africa
The ex-secretary general told the joint Houses of Parliament that hardly any region of the world escaped the slave trade's historical "stain".
But investment would help "turn the page", he said in an address marking the bicentenary of slavery's abolition.
Only 31 world leaders have addressed both Houses of Parliament since 1939.
Mr Annan described slavery as "an abominable practice taken to its most abominable extreme" and said the question should be asked why the trade was "tolerated for so long" in Britain.
Many Africans believed they had still not been compensated for the damage caused by slavery, he said.
And with Africa likely to be the only region of the world to not achieve the majority of the UN's Millennium Development Goals by 2015, he said the damage could best be addressed through investment in poverty relief.
"A bold investment in addressing poverty in Africa, as promised by the G8 in Gleneagles, would be the best way to heal the wounds of the past and turn the page," he said.
However, with thousands of women and children being sold and exploited globally every day, slavery still existed, he warned.
Many were "working in mines, sweatshops, brothels and plantations, trapped by debt and violence," he said.
"Slavery cannot be relegated to the annals of history so long as men, women and children are still being coerced, drugged, tricked, and sold to do dangerous and degrading work against their will."
But the work of abolitionists such as William Wilberforce and Thomas Clarkson demonstrated how crucial public opinion was in changing policy, he said.
"In the half-century following the Slave Trade Act, the Royal Navy freed almost 150,000 beings. Ideals that once seemed quixotic were backed with battleships.
"And so we revisit the history of the slave trade not only with horror but with hope."
At a high level meeting in Berlin last month, Mr Annan, who set up a panel to assess the West's aid pledges to Africa, warned that targets for the continent "would be missed" unless more was done.
In 2005, rich nations pledged to increase aid for developing countries by $50bn (£24.9bn), and eliminate debt of the 18 poorest nations in Africa.
Addressing the joint Houses of Parliament is considered an honour.
The list of those previously to do so includes Nelson Mandela, the Dalai Lama and former US presidents Bill Clinton and Ronald Reagan.