The UK high commissioner to Kenya has launched a scathing attack on President Mwai Kibaki's government's record on tackling corruption.
Kibaki based his 2002 election on the fight against corruption
Edward Clay said that corruption had cost Kenya some $188m since Mr Kibaki took office in December 2002.
He said corrupt ministers were "eating like gluttons" and "vomiting on the shoes" of donors.
Mr Clay was later summoned by Foreign Minister Chirau Mwakwere to "give facts and figures and to name names".
During a 30-minute private meeting, Mr Mwakwere said Kenya was disappointed by the high commissioner's remarks and angry that he had not followed diplomatic channels.
"We are disappointed, disappointed that Sir Edward Clay has failed to substantiate on the allegations that he made. He has refused to give us facts and figures," Mr Mwakwere told the BBC's Focus on Africa programme.
"Let him substantiate first, after that maybe it will be for me to apologise to him, in which case I won't mind, maybe it will be for him to apologise not just to me but to the nation, to the government to the people of Kenya and to the world."
Mr Mwakwere warned that if Mr Clay refused to substantiate his allegations by Thursday noon local time he would be "not only letting down the British government but also himself".
Mr Clay's criticism was also dismissed by Kenyan Vice President Moody Awori who said those who had evidence of wrong-doing should contact the police.
Meanwhile, an inquiry into corruption under ex-President Daniel arap Moi has released a list of 1,115 alleged beneficiaries of the so-called Goldenberg affair.
Mr Moi has always denied being part of a scam that involved re-exporting gold and diamonds, which is thought to have cost Kenya as much as $600m between 1990 and 1993.
Donors have restored aid to Kenya, suspended under Mr Moi because of worries about corruption but Mr Clay suggested that aid could again be withheld.
He said he realised that corruption would not end overnight with the change of government.
But "we hoped it would not be rammed in our faces," he told a lunch meeting for UK businessmen.
"They may expect we shall not see, or notice, or will forgive them a bit of gluttony because they profess to like Oxfam lunches."
The $188m would pay for 15,000 new classrooms - half the number the education ministry says it needs, the UK envoy said.
Among Mr Clay's other charges:
- A list of ministers and senior civil servants who were not corrupt would "fit on a postcard, or possibly a postage stamp".
- Attempts had been made to "kneecap" the body set up to fight corruption
- A contract worth more than $125m had been awarded to a company "incapable of commissioning a garden shed and discovered never to have delivered anything more than drawings more or less on the back of an envelope, and hot air".
MPs close to Mr Kibaki have accused foreign envoys of interfering in Kenya's affairs by criticising the government.
Lands, Settlement and Housing Minister Amos Kimunya said that people should focus on the government's efforts to fight the corruption it had inherited.
While Planning and National Development Minister Anyang' Nyong'o said: "One thing is certain, that I know the number of clean, well meaning ministers and civil servants can be written in an encyclopaedia, and not on the back of a stamp of a postcard."
Corruption watchdog Transparency International says that police corruption has fallen since Mr Kibaki took over in December 2002.
Mr Clay also said he hoped Kenya would have had a new constitution by now - Mr Kibaki had promised to introduce one within 100 days of taking office and the issue has divided his ruling coalition.