More than a year after 16 ponies died while being ferried across Bass Strait, criminal charges have been laid against the operator of the Spirit of Tasmania and two drivers.
The state government-owned TT-Line Company has been charged along with the drivers of two horse transport vehicles, following the deaths of the prized polo ponies during the crossing in late January 2018.
Tasmania's Department of Primary Industries on Wednesday said some of the Animal Welfare Act charges related to horses which survived the same journey between Devonport and Melbourne.
TT-Line and the driver of the vehicle in which the horses died allegedly failed to prevent unreasonable and unjustifiable pain and suffering to the animals.
Both drivers are also accused of failing to make sure the horses were kept in individual stalls.
In a statement, TT-Line said it would vigorously defend the allegations.
"We have been working closely with Biosecurity Tasmania for many months on animal transport and are surprised by the charges," TT-Line boss Bernard Dwyer said.
"We note the comments made by Biosecurity Tasmania immediately after the incident that the department was confident that there was not an ongoing risk for the transport of horses across Bass Strait and that it was an isolated incident."
The matter is due in Devonport Magistrates Court on August 1.
It follows a lawsuit launched last year over the deaths of 13 of the ponies.
The legal action, brought by polo identity Andrew Williams, accused TT-line and QUBE Holdings Limited of failing to provide a safe environment for the horses.
Mr Williams, his partner Rebecca Williams, Twynam Agricultural Group and Willo Polo, sought $739,000 in damages.
The horses died sometime between January 28 and 29 last year.
Australian Associated Press