A High Court judge rejected Mr Anwar's $26m case saying it was "frivolous, vexatious and an abuse of court process".

In April, Mr Anwar was found guilty of corruption and sentenced to six years in jail. He is now on trial again for sodomy.

He filed the defamation suit against Dr Mahathir in January, alleging his former boss had falsely and maliciously accused him of committing an immoral act.

PM Mahathir: His comments were "statements of facts", the judge ruled

Dr Mahathir said his words were published in his capacity as prime minister and were not meant to disparage Mr Anwar.

The judge said the case brought by Mr Anwar was "obviously unsustainable" and ordered him to pay the prime minister's legal costs.

The judge said that the prime minister's words were merely statements of facts already widely published before he made them.

After Mr Anwar was sacked, Malaysian newspapers published allegations that Anwar had committed sodomy - a crime in Malaysia - and other sexual offences.

Last September, Mr Anwar's adopted brother Sukma Darmawan and speechwriter Munawar Anees pleaded guilty in a court to being sodomised by Anwar.