The BBC has obtained evidence of a major corruption scandal in Kenya.
A former top anti-corruption official has given the BBC what he says is taped evidence of a government minister trying to impede a corruption inquiry.
John Githongo says he told President Mwai Kibaki about the corruption, but the president failed to act.
Kenya's cabinet is holding a crisis meeting in Nairobi and Kenyan MPs are to head to Britain to interview Mr Githongo about the allegations.
Mr Githongo, Kenya's former permanent secretary for ethics, says he made the tape secretly during a meeting with Kiraitu Murungi, who was Kenya's justice minister at the time of the meeting and who is now energy minister.
On the tape heard by the BBC, a man Mr Githongo says is the minister is heard telling him that the loan is owed to a businessman with links to powerful politicians and that if he goes slow on his investigation the businessman will also go slow.
"The minister of justice was telling me that if I eased off my enquiries then my father's loan matter would be made to go away," Mr Githongo said.
Mr Murungi would not be interviewed but denies wrongdoing.
Mr Githongo says government money was being paid to companies that did not exist or to others which were massively overpricing their contracts.
The scandal, known as the Anglo Leasing affair, has cost the Kenyan exchequer millions of dollars, according to Mr Githongo's investigations.
He believed the finance was being given to business figures close to the government, who were then re-directing some of it back to the ruling elite for political campaigning.
In one case, he says, the country's then-Justice Minister Kiraitu Murungi tried to pressure him by using the issue of a loan owed by Mr Githongo's father.
The Kenyan government has not reacted officially to Mr Githongo's latest allegations. A junior minister in the Department of Information, Koigi Wamwere, said that if Mr Githongo has allegations against Kenyan ministers, he should come back to Kenya and make his case.
"Let what you have to say be corroborated by others. Let those whom you are accusing challenge your words. So come home. This is the best theatre for that war, not where you are fighting it from."
Mr Githongo now lives in the UK and has said he feared for his safety if he were to return to Kenya.
UK International Development Secretary Hilary Benn described Mr Githongo as a "very courageous" man.
"He has now brought forward very, very serious allegations which have to be investigated... I think this is a moment of truth for Kenya," Mr Benn said.
The British minister said corruption had been a problem in Kenya for years but now John Githongo had "brought matters to a head".