Facing five years or more in jail on politically motivated charges, Dr Anwar, 67, says he ignored advice on recent travels overseas not to return to Malaysia where the government of Prime Minister Najib Razak has used colonial-era laws to investigate, charge and jail dozens of critics under its draconian Sedition Act.

"This is my village, my country. I cannot imagine, at this age, leaving," he said on the eve of the final stages of a so-called "sodomy" trial that human rights groups describe as a blatant attempt to end his political career and destroy his political alliance.

"But more pertinent is my desire to set a good example to Malaysians, particularly the young," he said.

Dr Anwar said he could not explain to young Malaysians how he could live comfortably overseas when Malaysians "have to endure the ignominy of authoritarian rule".

He has received offers of asylum from several countries, including the United Kingdom and Turkey.

A ruling this week in Dr Anwar's long-running sodomy case is likely to be a turning point for Malaysia as his Pakatan Rakyat (People's Alliance) looks to find a younger generation of politicians who will be able to pose a credible challenge to the United Malays National Organisation (UMNO)-led coalition that has held power in one form or another since 1955.

Dr Anwar held two unlikely partners – the Islamic PAS (Pan-Malaysian Islamic Party) and the secular and socialist DAP (Democratic Action Party) together as authorities in Kuala Lumpur relentlessly pursued him over sodomy charges that the High Court cleared him of in 2012.

The alliance won more votes than the government at gerrymandered elections last year but divides among the parties run deep, raising doubts they will be able to stay together without Dr Anwar, their unifying force.

Dr Anwar says he is "prepared for the worst" on the charge of sodomising a former male aid in 2008, a crime under which he has been charged four times but has only been invoked seven times since in the majority-Muslim country since 1938.

"Malaysia's sodomy laws seems to exist chiefly to persecute Anwar Ibrahim," said Phil Robertson, Asia's Watch's deputy director in Asia.

As well as going to jail Dr Anwar will be banned from contesting elections for years if the conviction is upheld.

Dr Anwar, a father of four, has been on bail since the Court of Appeal in March overturned an earlier acquittal and sentenced him to five years' jail.

A former firebrand student leader, he was sacked as deputy prime minister in 1998 after a bitter falling out with strongman prime minister Mahathir Mohamad, who ruled the country for 22 years.

Dr Anwar spent six years in jail on another charge of sodomy which was later overturned.

He believes the government will charge him of sedition if he is acquitted of the sodomy charges.

Authorities have been carrying out the broadest crackdown on the political opposition and social activists since the Mahathir era, despite that Mr Najib two years ago promised a path of greater openness for the country of 30 million people.

More than 40 opposition MPs, students activists, lawyers, academics and journalists have been investigated, charged or imprisoned under the Sedition Act this year.

The crackdown is seen as an attempt to silence opposition parties as a power struggle is under way in the ruling coalition.

Dr Mahathir, still a influential figure in UMNO, has withdrawn his support for Mr Najib.

The Federal Court began hearing Dr Anwar's appeal against the conviction on Tuesday.