In a statement on Friday, Basslink said Cable Consulting International, a UK-based firm regarded as a leading submarine power cable expert, was initially asked to conduct an inquiry into the cable failure.
A further independent investigation was carried out and the report was completed recently.
Basslink said the new report, known as the CCI Report, had come to the conclusion that the cause of the failure was unknown, refuting the charges made by Hydro Tasmania, a subsidiary of the government, and the state.
Since then, charges have been flung back and forth. On 20 December 2017, Hydro Tasmania said it had identified the cause of the Basslink failure and cited two experts who said it was because Basslink had exceeded its design limit.
But two days later, Basslink chief executive Malcolm Eccles dismissed the findings, saying that the expert reports cited as proof merely outlined one possible cause of the outage.
The CCI report had been provided to both Hydro Tasmania and the state, the Basslink statement said.
"Basslink has consistently maintained its position that the cable failure was a force majeure event under the Basslink Services Agreement and Basslink Operations Agreement," the statement said. "The recent CCI Report further supports Basslink’s view that the cable failure was a force majeure event under the BSA and BOA."