But it is unlikely to have any immediate impact as it will take months before any case is heard.

Najib has come under criticism over allegations of corruption linked to the debt-laden state fund 1Malaysia Development Berhad (1MDB) and deposits into his private accounts worth around $680mn.

He has denied any wrongdoing, maintains that he did not use the funds for personal gain and this year he was cleared of any criminal offence or corruption.

Mahathir accused Najib in the lawsuit of the "corrupt practice of carrying out various steps that were actively and deliberately taken in bad faith ... to obstruct, interfere, impede and derail the various investigations and inquiries which were being conducted by various legal enforcement agencies".

Najib's office did not immediately reply to requests seeking comment.

Mahathir was joined in the lawsuit by Khairuddin bin Abu Hassan and Anina binti Saadudin, former members of the United Malay National Organisation (UMNO) which Najib heads.

Mahathir on March 4 joined hands with long-standing foes, including the party of the jailed Anwar Ibrahim, to crank up pressure on Najib to quit.

In a dramatic flourish, Mahathir read a statement signed by 58 politicians and anti-corruption activists at a news conference where he was flanked by opposition leaders and some members of the ruling party he has now quit.

The plaintiffs in Wednesday's suit are seeking exemplary damages from Najib to the government of 2.6bn ringgit ($650mn) and aggravated damages of 42mn ringgit - equal to the amounts that were allegedly deposited into Najib's bank account.

Mahathir's lawyer, Haniff Khatri, told Reuters it would take three months for the court to decide if the case would be heard.

"We don't go with empty hands, (we) have material, witnesses and we are confident of the outcome," he said.

But political analysts weren't optimistic.

"The real impact is very limited in the sense of legal terms," said Ibrahim Suffian, director of independent opinion polling firm Merdeka Center. "This is going to be battle that is drawn out for a longer period."