Malaysian former Prime Minister Najib Razak starts his final attempt on Monday to set aside his conviction in a corruption case linked to the multi-billion dollar 1MDB financial scandal.

The country's highest court has scheduled hearings through Aug. 26 to hear Najib's appeal of his convictions for criminal breach of trust, abuse of power and money laundering over the alleged theft of $4.5 billion from 1Malaysia Development Berhad (1MDB), a state fund he co-founded as premier in 2009.

At least six countries have launched investigations into 1MDB, a global scandal that has implicated high-level officials and major financial institutions.

Prosecutors say more than $1 billion in 1MDB funds made its way into Najib's personal accounts.

Najib, 69, who has pleaded not guilty to dozens of charges, was sentenced in July 2020 in the first of several trials to 12 years in jail and a $50 million fine for illegally receiving about $10 million from SRC International, a former 1MDB unit.

The conviction was upheld by an appeals court last year.

In addition to appealing that verdict, Najib is asking the Federal Court to introduce fresh evidence to nullify the trial, accusing the trial judge of a conflict of interest, documents filed ahead of Monday's hearing showed.

Najib, who was voted out in 2018, has been free on bail pending the appeal. If the verdict is upheld, he would likely begin his sentence immediately, according to a prosecutor. Malaysian law allows for a review of Federal Court decisions, but such applications are rarely successful.

The appeal comes ahead of national elections that are expected to be called before a September 2023 deadline.

An acquittal could spark a political comeback for Najib, who told Reuters last year he had not ruled out seeking re-election to parliament.

While he remains a popular figure and active lawmaker, Najib is barred from contesting elections unless his conviction is overturned or he receives a royal pardon.