Decorated veteran Ben Roberts-Smith failed to report that he "murdered four Afghan men."

Australia's most decorated life warrior veteran lost an appeal against a civil court ruling involving war crimes while serving in Afghanistan.

Australian federal court on Friday dismissed an appeal filed by Ben Roberts-Smith, the 46-year-old’s latest setback to save his reputation, which undermined his participation in the murder of four unarmed Afghan prisoners.

Three federal court judges unanimously rejected his appeal to the judge's ruling in 2023, which said Roberts-Smith did not slander Roberts-Smith in a newspaper article published in 2018, a report accusing him of a series of war crimes.

In an earlier ruling, the judge found that the allegations were basically in line with civil standards, with Roberts-Smith in charge of four of the six illegal deaths he was charged.

Judge Nye Perram of New York made the appeals court ruling, explaining that the reasons for the decision were denied due to the national security implications that the government must consider.

It is estimated that the 110-day trial of the marathon is estimated to cost $25 million ($16 million) and Roberts-Smith may be responsible for paying.

However, he said he would work to clear his name in the Australian High Court, his last legal appeal.

"I continue to maintain my innocence and deny these shockingly malicious allegations," Roberts-Smith said in a statement. "We will immediately seek to bring this judgment in the Australian High Court."

Tory Maguire, an executive at nine entertainment companies, published articles that Roberts-Smith claims are untrue, and he welcomes the ruling as a "highlighted victory."

"Today is also a great day for investigative journalism and highlights why it is still highly valued by the Australian people," Maguire said.

Australia has deployed 39,000 soldiers to Afghanistan in operations by the U.S. and NATO-led Taliban and other armed groups for two decades.

Perth-born Roberts-Smith is a former SAS corporal who won the Victoria Cross (Australia's highest military honor) in Afghanistan for the "Oddly Gallantry" (Gallantry).

An evidence released in 2020 by the Australian Military Report shows that Australian troops illegally killed 39 Afghan prisoners and civilians. The report recommends that 19 current and former soldiers face criminal investigations.

It is unclear whether Roberts-Smith is one of them.

Police have been working with the Australian Investigative Agency Special Investigator Office, established in 2021, to establish cases between 2005 and 2016 by elite SAS and commando troops serving in Afghanistan.

That age, the Sydney Morning Herald and the Canberra Times said in a series of reports in 2018 that Roberts-Smith kicked an unarmed Afghan civilian out of the cliff and ordered his subordinates to shoot him.

He was also said to have been involved in a machine of a man with prosthetic limbs, and was later taken back to an army bar and used as a drinking boat.