Independent MP David O'Byrne has said he will support a no-confidence motion against embattled Treasurer and Deputy Premier Michael Ferguson over his handling of the roll-out of two new Spirit of Tasmania ferries and associated port upgrades if one was moved in state parliament this week.

Mr O'Byrne's decision on Sunday has meant there are enough votes from the crossbench for a no-confidence motion to succeed when parliament resumes on Tuesday, with Jacqui Lambie Network MP Andrew Jenner and independent Kristie Johnston having already called for Mr Ferguson to resign from parliament.

The Labor-turned-independent MP for Franklin is prepared to support the motion, saying there had been a "serious failure of policy and governance".

"I thought when Minister Ferguson relinquished his infrastructure portfolio that that contrition … was a statement from him as minister, that he took responsibility," Mr O'Byrne said.

Mr O'Byrne said he had informed the premier of his decision and has made it clear that if a no-confidence motion was passed that he expected the boards of TasPorts and Spirit of Tasmania operator TT Line to be stood down and administrators appointed.

Eighteen votes are required for the no-confidence motion to be carried.

The combination of the three crossbenchers along with Labor and the Greens, who together hold 15 seats in the 35-seat lower house, would be enough for the motion to be successful.

Mr Ferguson remains the second-most senior member of cabinet, remaining central to the machinations of government.

'No need for Mr Ferguson to resign', Abetz says 

Mr Ferguson has faced growing calls to step down from the frontbench over the troubled roll-out of the two new Spirit of Tasmania vessels and associated port upgrades, while he was the shareholder minister for TasPorts and ferry operator TT-Line.

A three-year delay to port upgrades at Devonport to berth the new ferries is expected to cost the state $300 million more than budgeted, with some interim upgrades still un-costed and delays in the new vessels so far costing an extra $88 million. 

If the no-confidence motion was successful, convention dictates Mr Ferguson would have to sit on the backbench and relinquish his ministerial portfolios.

He would also have to resign as deputy premier. 

However, this has been challenged by Minister Eric Abetz, who said Mr Ferguson had the "full support of his colleagues" and urged him not to resign from parliament.

"Even if a motion of no-confidence were to be passed in him … there will be no need for Mr Ferguson to resign and I would encourage him not to resign." 

Labor taking wait-and-see approach

Opposition leader Dean Winter said he would wait to see whether Premier Jeremy Rockliff asked his deputy to resign before deciding whether to move a no-confidence motion.

"He needs to go," Mr Winter said.

"We'll be talking to the crossbench and the parliament over the course of the next couple of days to make sure that we're in a position to hold this minister to account." 

Mr Winter described Mr Abetz's comments that a no-confidence motion would be inconsequential as "extraordinary". 

"Are they willing to trash years of constitutional convention in the Tasmanian House of Assembly?" he said.

"Are they prepared to trash Tasmanian democracy for this man? I don't think they should." 

On Sunday, Labor announced it intends to introduce legislation to change how state-owned businesses such as Hydro Tasmania and TasPorts are managed, if it wins the next election.