Kenya's former anti-corruption czar is considering returning home to testify to parliament, nearly a year after fleeing to the UK in fear of his life.
John Githongo resigned after receiving death threats
John Githongo has been asked by the government to appear before a parliamentary committee.
His latest allegations of corruption by four top ministers have threatened to bring down the government.
President Mwai Kibaki was elected in 2002 on a pledge to fight the corruption which has plagued Kenya.
Mr Githongo released a statement on Friday saying that he was "finalising the modalities and dates" of his return with the Kenyan authorities.
But he has told the BBC that he is not certain to return.
He resigned from his post in February 2005 and fled the country after receiving death threats.
On Thursday, the government said it would guarantee his safety.
Kenya's Minister for Lands Amos Kimunya told the BBC on Friday that the government was "firm and united in its fight against corruption".
"We call on John Githongo to return to Kenya to give evidence to the Kenya corruption committee on any matter he terms important regarding father investigations on corruption," he said.
Mr Githongo said he had received an invitation dated 23 January from the clerk of parliament, Mr SW Ndindiri, to "give further evidence as the issues were raised when [I served] as Permanent Secretary for Government and Ethics".
His 31-page report was leaked last weekend, saying his attempts to investigate the Anglo-Leasing scandal were blocked by four top ministers - Vice-President Moody Awori, Energy Minister Kiraitu Murungi, Finance Minister David Mwiraria and sacked Transport Minister Chris Murungaru.
President Kibaki is under increasing pressure over corruption
The money raised by the alleged scam was to be used to fund the ruling Narc coalition's campaign in elections due next year, Mr Githongo said.
Civil rights groups, church leaders and lawyers have urged Mr Kibaki to suspend the ministers until investigations are carried out.
Mr Murungi and Mr Awori have publicly denied the claims. The others have made no public comment.
Mr Murungi said the report was "untrue" and an attempt to bring down the government.
Following the leaking of the 31-page report, the opposition urged President Kibaki to dissolve cabinet.
Opposition Orange Democratic Movement leader Uhuru Kenyatta said: "This is clear evidence that the government can no longer be trusted to conduct detailed and honest investigations into this saga."