Tony Blair's expression of "deep sorrow" over the UK's role in the slave trade has received a mixed response.
Slavery had been 'profoundly shameful', Mr Blair said
Although some campaigners have called for a full apology, others have said the PM's statement was enough.
The editor of New Nation, the newspaper which published Mr Blair's comments, said it was right to acknowledge the wrong and "now we can move on".
But campaigners Anti-slavery International said they would like to see Mr Blair "going a bit further".
Mr Blair's comments come ahead of official commemorations to mark the 200th anniversary of the abolition of slavery.
He said it was a "profoundly shameful" occurence, but the government has ruled out a formal apology.
Mr Blair said: "It is hard to believe what would now be a crime against humanity was legal at the time.
"I believe the bicentenary offers us a chance not just to say how profoundly shameful the slave trade was - how we condemn its existence utterly and praise those who fought for its abolition - but also to express our deep sorrow that it could ever have happened and rejoice at the better times we live in today."
Deputy Prime Minister John Prescott has been drawing up ideas for the 25 March anniversary, including the possibility of a "statement of regret" for Britain's involvement.
The director of Anti-slavery International, Aidan McQuade, said: "It's good enough saying that you're sorry but we'd like to see concrete actions in place in relation to addressing the legacies of the Trans-Atlantic slave trade."
He specifically wanted to see the history of the slave trade as a compulsory part of the national curriculum.
"They could also make measures of reparation towards the communities and countries which have been impoverished and devastated by the Trans-Atlantic slave trade, and they could have much more concrete measures in terms of eradicating contemporary forms of slavery in the world today."
Describing the trade as "possibly the biggest episode of inhumanity from man to man," New Nation editor Michael Eboda said it was important for Britain to acknowledge its role.
"It's only right that because of the magnitude of the wrong that it did, that at some stage it sort of recognises that and says we hold our hands up and we're sorry we did that, and now we can move on."
Trevor Phillips, head of the Commission for Racial Equality, welcomed the prime minister's statement.
Mr Phillips said his own family had traced its roots back 150 years - and his great-great-grandmother was born into slavery and given the name "Happy" by her masters.
"Like all the descendents of the 12 million and more Africans whose ancestors were kidnapped, brutalised and slaughtered, our family has waited centuries for someone in Europe just to acknowledge what was done to us.
"We will never have our true names back, we can never really be compensated. But this recognition matters."
However, other campaigners for reparation were disappointed at the limited scope of Mr Blair's comments.
Esther Stanford, the secretary of the Rendezvous of Victory Campaign, said: "This statement of regret does not go far enough.
"What is now required is a dialogue about how we repair the legacies of enslavement, and we're talking about educational repairs, we're talking about economic repairs, family repairs, cultural repairs, repairs of every kind that we need to recreate and sustain ourselves - it will cost."
A race advisor to London's mayor said the comments would anger some activists.
Lee Jasper said: "That may well infuriate the descendants of enslaved Africans who want and deserve a full and unfettered apology for what is one of the greatest crimes in human history, so I think it could be a halfway measure which would satisfy not a lot of people."
Culture minister David Lammy said that he "did not want to get into a blame fest" but wanted next year's events to celebrate the people who abolished the trade and commemorate those who died.
"In Tony Blair's statement today he recognises that there is a legacy from this period of history in Africa and that there is a legacy in relation to black people living here in Britain."
He stressed that the Labour Party had always focused on equality and would continue to fight against modern slavery.
"Tony Blair has gone further than any other leader of any western democracy," Mr Lammy said.
"He has struck the right balance between providing for the future, commemorating the past and moving forward as a multi-ethnic nation."