This is in addition to the 32 criminal charges he already faces for money laundering and graft.
His former treasury chief Irwan Serigar Adbullah was also charged with breach of trust. This makes him the highest-ranking civil servant to be charged since Najib was ousted in May’s general election.
They have both pleaded not guilty to all the charges, which each carry a jail term of up to 20 years, a financial penalty and a whipping sentence. But Najib and Irwan could be exempt from the latter as they are over the age of 50.
The new government, led by Mahathir Mohamad, has been cracking down on corruption and several former government officials have been charged.
Billions of dollars have gone missing from state fund 1Malaysian Development Berhad (1MDB), founded by Najib in 2009, which has been in the spotlight of the administration’s investigations.
“Nothing in the charges show that any of the acts I undertook resulted in any benefit to me,” Najib said at a press conference after the court hearing.
“There shouldn’t be any belief that any of the monies stated in the charges were lost, or that there were any elements of self-interest.”
Four of the six new charges relate to a settlement agreement between the state fund and Abu Dhabi state fund IPIC, Azam Baki, a deputy commissioner at the anti-graft agency said.
Last year, the 1MDB agreed to pay $1.2bn to the Abu Dhabi fund, in a settlement agreement following a dispute between the two over bond payments.
The 1MDB charges allege that Najib and Irwan committed the breach of trust offence with 220m ringgit ($7.4m) of government funds meant for Kuala Lumpur International Airport Berhad, 1.3bn ringgit ($440m) for a subsidy and cash aid programme and 3.3bn ringgit ($1.1bn) of other government funds.
The judge released both men after setting a bail of 1m ringgit ($339,000) each.
The former prime minister has been charged with money laundering related to three transfers totalling $10m into his personal bank account. Properties linked to Najib were also raided in June and police seized goods and cash worth up to $273m.
Najib’s wife was also charged with money laundering and tax evasion as part of a corruption investigation earlier this month.
The 1MDB scandal erupted in 2015 after media reported that hundreds of millions of dollars from the fund had been diverted into Najib’s personal accounts.
But Najib has consistently denied any wrongdoing and said that the funds were donations from a Saudi royal and had been given back.
After the anti-graft agency reopened the investigation, it was found that earlier investigations were obstructed by the former government.