David Cameron has hailed the anti-corruption summit he is hosting in London as "the biggest demonstration of the political will to address corruption that we have seen for many, many years".
The summit has brought together more than 40 countries including 12 heads of state and government.
Speaking at the end of the first day, he said attendees had shown "far more political will not just for words, but for action that will make a difference".
David Cameron's comments on corruption in Nigeria and Afghanistan are "very unhelpful and deeply regrettable", Nigerian poet and novelist Ben Okri has told ITV News.
Mr Okri said he was "appalled and rather surprised" that the prime minister would make the remark, saying it sent out the wrong signal and would damage relations between the nations.
Mr Okri, considered one of the foremost African authors, described the comments as "fantastically" unhelpful.
He said: "I'm rather appalled actually and rather surprised that a leader of an important world nation should be making that kind of remark to world. I think it sends a very wrong signal out to the world, I think it's a very discouraging remark."
He added that he thought Mr Cameron should apologise, saying: "I think he should make sensible amends."
David Cameron hoped to sign up a global declaration against corruption - but only six countries put pen to paper.
Why is it happening? Who is going? And will it get awkward after the Prime Minister's 'corruption gaffe'?
David Cameron has praised Nigeria and Afghanistan for the action they have taken in combating corruption.