Amralah, the horse at the centre of a law suit brought by his owner Lloyd Williams against a veterinary clinic, has been officially stripped of his Listed win in Adelaide.

Williams is taking action against Ballarat vet Brian Anderson for the loss of earnings after Amralah had to be taken out of the Melbourne Cup because of ongoing positive tests to a prohibited drug.

A post-race sample taken from Amralah after he won in Adelaide on September 19, showed the presence of Dexamethasone.

Amralah was free of the substance when he won the Herbert Power Stakes on October 10 which propelled him up the markets for the Melbourne Cup.

But subsequent tests between October 27 and November 16 showed the substance was still in his system.

According to the writ, Anderson injected Amralah on September 4 with a long-acting cortisone known as Dexafort, which contains Dexamethasone, and advised it would take 14 days to leave the horse's system.

He was treated again after the Herbert Power.

The writ claims Dr Anderson and the Ballarat Veterinary Practice failed to exercise reasonable skill and care and failed to ensure the treatment did not prevent Amralah from racing.

South Australian stewards this week disqualified Amralah from his win and fined trainer Robert Hickmott $8000.