The lawyers' forum in Malaysia has approved a motion seeking the resignation of Attorney-General Mohd Apandi Ali over his stance in the corruption probe against Prime Minister Najib Razak.

"Around 700 (in favour). Passed already," a source within the Malaysian Bar Association told Malay Mail Online.

The motion asks Ali to step down over his handling of cases involving 1Malaysia Development Bhd (1MDB), former 1MDB unit SRC International and the transfer of more than $800 million into the prime minister's account.

Najib is reeling from allegations that he diverted hundreds of millions of dollars from the state-owned company into his personal account in the run up to the 2013 election.

More than $1 billion was deposited into Najib's account between 2011 and 2013, the Wall Street Journal reported last week, citing people familiar with the ongoing investigations.

Attorney-General Mohamed Apandi cleared Najib of any wrongdoing in January, saying the money deposited in the prime minister's bank account was entirely legal "personal donation" from the Saudi royal family.

Swiss prosecutors said later about $4 billion was stolen from Malaysian state fund 1Malaysia Development Berhad (1MDB).