Kenyan Finance Minister David Mwiraria has resigned after being linked to a corruption scandal that has shaken the Kenyan government.
David Mwiraria was accused of warning off investigations into Anglo Leasing
The multimillion dollar "Anglo Leasing" corruption scam involved contracts for a company that existed in name only.
Mr Mwiraria, who is one of President Mwai Kibaki's key allies, has said the allegations against him are false.
The former anti-corruption tsar who made the allegations says he will testify before Kenyan investigators.
President Kibaki has come under pressure from donors to live up to his 2002 poll pledge to curb corruption.
Mr Mwiraria said he was stepping aside in order to clear his name, after he was mentioned in a report by the government's former anti-corruption chief John Githongo.
The 31 page report, leaked just over a week ago, alleges that he and three other top ministers blocked investigations into the Anglo Leasing scandal.
"The allegations made against me... cast serious aspersions on my character and integrity, have greatly disturbed me," said Mr Mwiraria, reading his resignation letter live on Kenya television.
Mr Githongo resigned a year ago, amid reports that his life had been threatened because of his corruption work.
He accuses the ministers of having links to a huge contract given to a non-existent company, Anglo Leasing, to print new high-technology passports, and build navy ships and forensic laboratories.
In a copy of the report obtained by the BBC, Mr Mwiraria, it is alleged, told Mr Githongo that it was felt he should "go easy" with his investigations into the affair.
Later it emerged that Mr Mwiraria allegedly knew that a well-known Kenyan businessman, whose involvement in previous government deals has raised serious questions, was also linked to Anglo Leasing.
The BBC's Karen Allen in Nairobi says Mr Mwiraria's is the first-high profile resignation.
Githongo alleges the president knew about the scam but did nothing to stop it
The other ministers mentioned in the report were Vice-President Moody Awori, Energy Minister Kiraitu Murungi and sacked Transport Minister Chris Murungaru.
Mr Murungi and Mr Awori have also publicly denied the claims.
Civil rights groups, church leaders and lawyers had urged Mr Kibaki to suspend the ministers until investigations are carried out.
Mr Mwiraria requested that investigations were made into the Anglo Leasing affair "so that the truth and the facts of the matter can be established".
"As I step aside, my conscience is clear that I have served the Kenyan people with dedication and honesty, and have not been party to any irregularity, criminal or unethical conduct," he said.
John Githongo says he stands by his allegations
Mr Githongo has agreed to testify before parliament's public accounts committee and also co-operate with Kenya's anti-corruption commission.
And in response to Mr Mwiraria's resignation, Mr Githongo said that he stood by his report, which he alleges, proves Mr Mwiraria was a key player in the Anglo Leasing scandal.
International donors have urged Kenya's president to take tough action against any cabinet ministers found to be corrupt.
The World Bank has delayed the release of $260m in loans to the country because of corruption allegations.
In his report, Mr Githongo said President Kibaki had known about the Anglo Leasing scam but had done nothing to stop it.