KUALA LUMPUR, Malaysia (AP) — Malaysian lawmakers took their oath in Parliament on Monday, including former Prime Minister Najib Razak, who has been charged in a massive corruption scandal that led to his coalition’s electoral defeat.

The swearing-in ceremony of 221 lawmakers opened the first Parliament session after Najib’s long-ruling coalition was ousted in May 9 elections, ushering in Malaysia’s first change of power since independence from Britain in 1957.

Prime Minister Mahathir Mohamad, the world’s oldest leader at 93, made his return to Parliament for the first time in 15 years after ending his retirement to challenge Najib over the corruption scandal.

Najib won his parliamentary seat despite his coalition’s defeat. A lawmaker is only disqualified if convicted and sentenced to more than a year in jail or fined over 2,000 ringgit ($494).

“I accept it because I want to serve the people. I want to be a constructive opposition member and play a role to ensure that democracy in our country is meaningful and healthy,” Najib told reporters when asked how he felt sitting on the opposition bench.

Najib, 64, pleaded not guilty earlier this month to charges of criminal breach of trust and abuse of power. His court case is linked to the 1MDB state investment fund that he set up when he took power in 2009 but which accumulated billions in debts and prompted investigations in the U.S., Switzerland and several other countries.

Mahathir had reopened investigations into 1MDB that were stifled under Najib’s rule, and barred Najib and his wife from leaving the country.

Najib denies any wrongdoing and has accused the new government of pursuing a vendetta against him. Police have also seized jewelry and valuables valued at more than 1.1 billion ringgit ($273 million) from properties linked to Najib.

U.S. prosecutors allege that Najib’s associates looted and laundered at least $4.5 billion from the fund. Switzerland’s attorney general indicated last month that the fraud could involve as much as $7 billion.

Earlier, Najib and dozens of opposition lawmakers briefly walked out over the appointment of the new lower house speaker, a retired judge. Najib said the walk-out was not a rejection of the new speaker but the government’s failure to give a 14-day advance notice to the house on his appointment.

Only one of the 222 lawmakers in Parliament was absent for the swearing-in, Home Minister Muhyiddin Yassin, who is recovering from surgery.