KUALA LUMPUR - Former Malaysian premier Najib Razak will file fresh civil suits against three investigators of a multi-billion dollar scandal at state fund 1MDB, after he withdrew his earlier applications against them on Monday.

Najib and his family have faced intense scrutiny since a shock defeat in a May election by his former mentor-turned-foe, Mahathir Mohamad, who reopened an investigation into 1Malaysia Development Berhad (1MDB) after becoming prime minister.

Najib's initial suits came days before he was arrested and charged over suspicious transactions at SRC International, a former unit of 1MDB. Najib, who has consistently denied any wrongdoing regarding 1MDB and SRC, pleaded not guilty.

The three suits were withdrawn after pretrial hearings to allow Najib to file fresh suits, state news agency Bernama on Monday quoted lawyer Alice Loke Yee Ching, who was acting for the government, as saying.

A spokesman for the law firm representing Najib, Badrul Samad Faik and Co, told Reuters it needed to make changes reflecting recent developments regarding its client's criminal charges before filing new applications.

In the three civil filings, Najib's lawyers accused anti-graft chief Mohd Shukri Abdull, police commercial crimes head Amar Singh and Attorney General Tommy Thomas of prejudice against the former prime minister.

Najib's law firm had earlier told Reuters it was seeking a court decision whether there was "an element of conflict of interest" among those handling the case.

Shukri declined to comment when contacted by Reuters, while Amar did not immediately respond to telephone calls or messages to seek comment. The attorney general's office did not immediately respond to an emailed request for comment from Thomas.

Last week, media reported Shukri as saying he would face any civil suit filed by Najib, while Amar told reporters the police would "respond accordingly" if there was a need. ($1=4.0450 ringgit)

(Reporting by Joseph Sipalan; Editing by Clarence Fernandez and Nick Macfie) ((Joseph.Sipalan@thomsonreuters.com; +60323338019; Reuters Messaging: joseph.sipalan.thomsonreuters.com@reuters.net))