An animal welfare adviser to the Tasmanian government is quitting over what he perceives as a lack of progress and deep-seated issues with the way investigations are handled.

Dr Malcolm Caulfield, the principal solicitor for the Melbourne-based Animal Law Institute, says the Department of Primary Industries has been keeping his committee in the dark about animal welfare cases.

This comes after a lack of information about the cause of death of 16 polo ponies in the back of a truck while crossing the Bass Strait on a ship in January.