TasNetworks on Wednesday released a business case on the proposed $3.5 billion Marinus Link which it said stood up technically and commercially.

But the report said Australia's energy pricing framework needed reform to ensure Tasmanian electricity users did not pay higher electricity prices once the interconnector came online for the benefit of mainland customers.

Labor's finance spokesman David O'Byrne said the report raised more questions than it delivered answers.

"The government can't say who will pay or how we will pay," Mr O'Byrne said.

He said the federal government was silent on changes to national rules to ensure Tasmania was burdened with the cost of the link.

Mr O'Byrne said it was naive to think other states would pick up the bill.

TasNetworks chief executive Lance Balcombe said the second stage of the plan, the design and approvals stage, would determine funding for the project.

This stage of the project is estimated to take three years to complete.

Mr Barnett said it was expected questions over finance and ownership would be answered by late 2021.

"The government will also ensure Tasmanians only pay their fair share for what is strategic national infrastructure benefiting the nation," he said.

"At the recent COAG energy council, we agreed to task the Energy Security Board to prepare advice on a fair cost allocation methodology for interconnectors."

Cradle Coast Authority chief executive Daryl Connelly said the project would transform prosperity for the North-West region.

"Thousands of jobs are likely to be created not only during construction but as a result of further wind and hydro investments that will become viable," he said.