By Guy Faulconbridge
British Prime Minister David Cameron has been filmed telling Queen Elizabeth that leaders of some "fantastically corrupt" countries, including Nigeria and Afghanistan, will attend his anti-corruption summit.
Cameron is hosting an international anti-corruption summit on Thursday (local time) aimed at stepping up global action to combat corruption in all walks of life.
In a pooled video feed made available to the ITN broadcaster, Cameron is shown talking with the queen about the summit.
"We had a very successful cabinet meeting this morning, talking about our anti-corruption summit," Cameron said when the queen approached.
"We have got the Nigerians -- actually we have got some leaders of some fantastically corrupt countries coming to Britain."
Cameron went on: "Nigeria and Afghanistan -- possibly two of the most corrupt countries in the world."
The queen, who steers clear of political comment, did not respond to Cameron's comment.
But the Archbishop of Canterbury, Justin Welby, said: "But this particular president is actually not corrupt."
Nigeria's President Muhammadu Buhari and Afghan President Afghan President Ashraf Ghani are both attending the summit and acknowledge corruption in their countries and pledge to clean it up.
Afghanistan is second-from-bottom in campaign group Transparency International's latest Corruption Perceptions Index, an annual ranking of countries.
North Korea and Somalia are jointly ranked worst at number 167, while Nigeria is ranked 136.
Cobus de Swardt, Managing Director of Transparency International said there is no doubt both Nigeria and Afghanistan have very high rates of corruption.
"But the leaders of those countries have sent strong signals that they want things to change."
It's not clear whether Cameron realised he was being recorded at the event at Buckingham Palace.
After Cameron's remarks about Nigeria and Afghanistan, John Bercow, the speaker of parliament's House of Commons joked: "They are coming at their own expense one assumes?"
Cameron's Downing Street office said both Buhari and Ghani acknowledged they faced a challenge to tackle corruption and had been invited to the summit because they are leading the fight against graft.
"In a collection of essays on the fight against corruption to be published on the day of the Summit, President Ghani writes that Afghanistan is 'one of the most corrupt countries on earth'," a spokeswoman for Cameron said.
"President Buhari writes that corruption became a 'way of life' in his country under 'supposedly accountable democratic governments'."