Mr Sukma and Mr Anwar's speechwriter, Munawar Anees, were convicted in September of allowing themselves to be sodomised by the former deputy premier between March 1993 and April 1998. They were both sentenced to six months in jail a day before Mr Anwar was himself arrested.

But on Tuesday Dr Zahari Noor said he found "no evidence of anal intercourse" when he examined Mr Sukma in early September.

South-East Asia Correspondent Simon Ingram: Sordid details have shocked a largely conservative nation

Dr Zahari said he had seen "no evidence of any injuries whether recent or old" and concluded there was no medical evidence that Mr Sukma had been penetrated by a "blunt object".

The revelations add yet more salacious details to a trial that has gripped Malaysia - a normally conservative country that frowns upon even the mildest public displays of affection.

'No evidence of intercourse'

Kuala Lumpur High Court: Scene of Malaysia's trial of the century

"So in layman's terms, you're saying there seems to be no history of homosexual relations," asked defence lawyer Christopher Fernando.

"I would say there was no evidence of anus intercourse," Dr Zahari confirmed.

Mr Anwar is currently on trial on four counts of corruption related to allegations that he used his position to cover up claims of heterosexual and homosexual misconduct. He denies all the charges.

Questionable methods

Earlier, Dr Zahari testified that police had used "highly questionable" procedures in collecting DNA samples from Mr Anwar's blood.

He said police did not request samples for DNA testing until two and a half months after blood had been taken to test for a range of sexually transmitted diseases.

The prosecution is expected to call DNA experts to testify that samples taken from Mr Anwar matched semen stains found on a mattress produced as evidence two weeks ago. The defence is now trying to prove that Mr Anwar never gave permission for DNA samples to be taken.