AIG has won a preliminary injunction against former CEO Chairman Maurice “Hank” Greenberg that bars his insurance business, Starr Technical Risks Agency, from writing policies for AIG customers on behalf of anyone other than the insurer.

The giant US-based global insurer has accused Starr of trying to siphon off the insurer’s business and pass it on to competitors.

It also blocks Starr from entering into reinsurance contracts with National Indemnity Co, a unit of Warren Buffett’s company Berkshire Hathaway.

AIG and Mr Greenberg have been at loggerheads since Mr Greenberg’s forced retirement from the company amid state and federal investigations into the company’s accounting practices last year.