An expert has warned the legal battle over the Basslink power cable failure could last several years.

In the most recent round of the legal fight over the 2015 Basslink failure, Hydro Tasmania said an expert report the Basslink commissioned that found the cable was being overused the cable and was at risk of degradation.

But Basslink says the cause for the power cable failure is still unknown.

Tasmanian energy expert Marc White says the back-and-forth is likely to drag on for some time.

“We were sold a product that's meant to do one thing, and now Hydro's experts have called into question whether the project can actually deliver on that over the next twelve years of the agreement,” Mr White told the ABC.

“We expect this will now play out in a legal battle for in excess of two years.”

He said the implications would reach across the water to Victoria, which buys some of its power from Hydro.

“Victorians have been expecting to rely on 630MW of peak power over summer, and if that's reduced to 500MW that will have significant impacts on how Victoria sources that power on the hot days of summer,” Mr White said.