The operators of the Spirit of Tasmania ferries say all options are on the table to replace the ships, including changing their route.
TT-Line directors company faced a parliamentary hearing this morning.
Questions on their plan to replace the ageing Spirit of Tasmania ferries dominated the session.
Chairman Michael Grainger says the State Government has placed no constraints on the investigation.
"The Government has left it up to us," he told the hearing.
Infrastructure Minister David O'Byrne quickly intervened.
"Apart from the Devonport bit." He says the Government is not willing to change the home port from Devonport.
"We're in agreement on the place where we have our Spirits, and that is the Devonport to Melbourne run," he aid.
"What the chairman is doing is the process around due diligence and ensuring that all options are put on the table to investigate." But Mr Grainger insists nothing has been ruled out, including moving from a two-ship service.
"We have engaged consultants to provide us with information on different port options, different route lengths." The directors of the state-owned company must recommend options for the service's future by December next year.
Mr O'Byrne says the Government has the final say on how the Bass Strait ferries are replaced or upgraded.
Wages questioned The TT-Line was also forced to defend the wages of its senior staff and directors.
The Opposition's Rene Hidding asked why the wages bill for senior staff and directors had increased by 40 per cent since 2007.
Mr Grainger says the growth is due to managers failing to take leave, not pay rises.
He says a new risk and resilience manager position has also been created to adhere to new occupational health and safety.
"We make no apologies, Mr Hidding, we make no apologies for the remuneration that our senior executives are paid," he said.
"As I said, it's benchmarked, it's not out of the ordinary for a company this size." The ferry service had 20,000 fewer passengers last financial year compared to the previous period, a drop of 16 per cent.