Malaysian ex-leader Najib Razak's first trial linked to the 1MDB scandal will proceed after a judge ruled Monday prosecutors had made a sufficient case, boosting efforts to bring him to justice over the mammoth fraud.

The former prime minister will take the stand next month when his defence begins, in the case related to the theft of billions of dollars from sovereign wealth fund 1MDB.

His coalition was ousted at the polls last year after six decades in power, largely due to the scandal, and he has since been arrested and hit with dozens of charges linked to the looting of the investment vehicle.

The 66-year-old went on trial for the first time in April over the controversy, in a case centring on the transfer of 42 million ringgit ($10.1 million) from a former 1MDB unit into his bank account. Najib denies any wrongdoing.

Prosecutors finished presenting their evidence in August, and on Monday High Court judge Mohamad Nazlan Mohamad Ghazali ruled the case was strong enough to go forward and Najib should enter his defence.

"The accused had enormous and overarching influence" over the 1MDB unit, SRC International, the judge told the court, adding the prosecution had established Najib has a case to answer for all seven charges he is facing.

Malaysia's former prime minister Najib Razak is accused of making millions off the mammoth 1MDB fraud
Malaysia's former prime minister Najib Razak is accused of making millions off the mammoth 1MDB fraud AFP / Mohd RASFAN

"It was under the control of the accused from day one. The accused wielded considerable power."

The alternative would have been to strike out the charges in the case -- although Najib is still facing several other cases linked to 1MDB, with his biggest trial over the scandal having opened in August.

Monday's decision will be a relief for Malaysia's government and 94-year-old Prime Minister Mahathir Mohamad, who came to power partly on a pledge to get to the bottom of the 1MDB scandal and bring those involved to justice.

Lawyers for Najib, who is free on bail, said he would take the stand when the defence stage of proceedings gets underway on December 3.

"I am calm and cool," the blue-blooded former leader, whose father and uncle were both prime ministers, told AFP after the ruling, giving a smile.

Factfile on the 1MDB scandal in Malaysia.
Factfile on the 1MDB scandal in Malaysia. AFP / John SAEKI

But his lead lawyer, Muhammad Shafee Abdullah, said that Najib was "shocked" by the court's decision, adding the ex-PM had been confident of being cleared.

And he indicated the legal saga may have some time to run, saying that appeals could push the case beyond Malaysia's next election -- due by 2023 at the latest.

Najib is facing four charges of corruption and three money-laundering counts in the trial.

Each charge of corruption carries a maximum jail term of 20 years, and each money-laundering count is punishable by a term of up to 15 years.

The amounts involved in Najib's first trial are small, however, compared to those in his second and most significant one, which centres on allegations he illicitly obtained over $500 million from 1MDB.

US authorities, who are investigating the fund as money was allegedly laundered through the American financial system, believe $4.5 billion was looted from 1MDB.

It was allegedly used to fuel a worldwide spending spree by Najib and his inner circle -- including suspected mastermind, fugitive financier Jho Low -- with looted cash spent on items ranging from a super-yacht to high-end real estate.

Following the election, police discovered valuables, including cash, jewellery and luxury handbags, worth up to $273 million in properties linked to Najib and his widely reviled wife, Rosmah Mansor.

Investment bank Goldman Sachs has become embroiled in the scandal over its role in helping arrange bond issues for 1MDB. Malaysia has charged three units of the bank, as well as current and former staff, claiming that large sums were stolen during the fund-raising.

The bank says it will fight the charges.