The setback was compounded by evidence of additional sexual crimes that drew gasps from the public gallery.

Mr Anwar's lawyers had asked the judge to throw out the evidence of key witness Azizan Abu Bakar after he appeared to contradict his statement that the former cabinet minister sodomised him in 1992.

The BBC's Helen Sawyer: "A significant legal setback for Mr Anwar"

But on Thursday Mr Azizan told court the confusion had arisen because he had misunderstood a lawyer's question.

Mr Azizan, who worked as Mr Anwar's driver, says his one time boss repeatedly sodomised him and made him a "homosexual slave".

Mr Anwar maintains his innocence

The accusation is central to the government's case against Mr Anwar, who has pleaded not guilty to five counts each of corruption and sodomy.

On Monday Mr Azizan apparently contradicted himself under cross-examination when he agreed with the defence that he had visited Mr Anwar's family between 1992 and 1997 because Mr Anwar did not sodomise him.

But under re-examination by the prosecution, the ex-driver said he had misunderstood the question because the year 1992 was ''too general''

"The sodomy act indeed happened to me while I was working as driver for the wife of the accused from early 1992 to May 1992," he added.

Shock new allegations

Mr Azizan said he remembered one incident at the home of Mr Anwar's adopted brother, Sukma Darmawan.

"One incident that I cannot forget is in the house of Sukma... where the accused sodomised me first after which his adopted brother sodomised me," he said, drawing gasps from the gallery.

The commotion was so great, a court bailiff warned members of the public to leave if they wanted to comment on the proceedings.

Mr Sukma and one of Mr Anwar's former speechwriters were both sentenced to six months in jail in September after pleading guilty to being sodomised by Mr Anwar.

They have since lodged appeals, saying police coerced them into the guilty pleas.

The new allegations came after Judge Augustine Paul rejected a defence motion to have Mr Azizan impeached, or disqualified, as a witness.

"It is meaningless to hold proceedings to impeach," he added.

The defence had argued that Mr Azizan had contradicted himself while on the witness stand.