Gatto takes defamation action against ABC

Melbourne underworld figure Mick Gatto claims he's been defamed by the ABC and has launched legal action against the national broadcaster.

Mr Gatto on Monday told AAP the matter was before the courts and "I can't elaborate", but the case is understood to stem from a February report published online in connection with Melbourne's gangland 'Lawyer X' scandal.

The news report was based on a 2016 police affidavit.

On February 12 Mr Gatto's lawyer issued a statement denying his client had ever threatened to kill Lawyer X, also known as "informer 3838", subsequently revealed as criminal lawyer Nicola Gobbo.

The statement also denied involvement in the deaths of drug trafficker Victor Peirce and grocer Frank Benvenuto.

"Not only is the reporting false, it is mischievous and damaging to Mr Gatto. As a result, my client is considering his legal position," lawyer Martin Amad said in February.

It's understood Mr Gatto has subsequently lodged a writ in the Supreme Court.

The ABC has been contacted for comment.