Tasmania's two federal independents have combined in an unlikely alliance to push for a better freight subsidy deal for the state.

Senator Jacqui Lambie, formerly from the Palmer United Party, has found common ground with Denison MP Andrew Wilkie.

The pair appeared together at a media conference in Canberra urging the Commonwealth to extend the Bass Strait subsidy to northbound freight.

They also want the Federal Government to drop plans to allow foreign workers to staff Bass Strait ships.

Earlier, Mr Wilkie welcomed Tasmania's newest independent Senator.

"I think its great news that Jacqui has now become an independent, she will be a more effective advocate for Tasmania," he told 936 ABC Hobart.

"I disagree with Jacqui on a lot of issues but I've got to know her and I work with her to some degree and I'll tell you it's hard to find a more passionate advocate for Tasmania both publicly and privately."

Mr Wilkie said tensions between the Senator and the Prime Minister over Defence Force pay would not detract from their campaign to get a better deal for Tasmania.

He dismissed the Prime Minister's refusal to meet her as political theatre.

"I think what is going on with the Prime Minister at the moment is just political theatre and the Prime Minister is just tyring to put Jacqui in her place, but frankly it is not in the public interest," he said.

Freight issue 'an absolute killer' for Tasmania's economy

There are already two equalisation schemes in place to make it cheaper for Tasmanians shipping to and from the mainland.

Mr Wilkie said he agreed with the Senator that the cost of freight was the biggest single handicap for Tasmania's economy.

He called for the Tasmanian Freight Equalisation Scheme (TFES) to be extended to cover exports from Tasmania to mainland Australia.

"That will obviously cost the taxpayer more money, but the point is it will save money in the long run because as we unlock the potential in the Tasmanian economy when we get people into work and we get people into good jobs then we will diminish the reliance on other government handouts, in particular Centrelink handouts," he said.

Senator Lambie said previous governments were also to blame for not fixing the issue.

"This has been going on both through Liberal and Labor for year after year after year and it is absolutely a killer down there for Tasmania," she said.

But the independent team's shared cause is doomed to fail.

The Commonwealth has not publicly ruled out changing the subsidy, but has declared it will not allocate any new money to extend it.

The Tasmanian Government had backed calls for the subsidy extension, but on Tuesday the state Infrastructure Minister, Rene Hidding, said the Commonwealth had been clear on its position in private discussions.

"The Productivity Commission did an inquiry into it, and their report is in the hands of the Federal Government," he said.

"Their response to the possibility of an extension of northbound export freight being covered under the Freight Equalisation Scheme is that the funds are not available.

"That's the response to the Tasmanian Government in that space. I need to move forward with our plans to institute a direct international shipping service," Mr Hidding said.

"We have a definitive response. There is no money on the table for TFES."

Mr Hidding has now also confirmed he has signed a Memorandum of Understanding with Singapore-based shipper Swire, and is hopeful a direct international service between Bell Bay and Singapore and some Chinese ports would start in 2015.

Move to roll back rules over shipping pay

Mr Hidding has also thrown his support behind a controversial plan to roll back the so-called "cabotage" laws introduced under the previous federal Labor government.

Mr Hidding's federal counterpart, Warren Truss, is considering a review of coastal shipping that recommends allowing foreign-flagged ships to service domestic shipping lines.

Unions fear that could lead to poorly paid foreign workers competing with ship workers earning Australian wages.

But Mr Hidding thinks the change would be in Tasmania's best interests.

"All Tasmanian federal representatives should be backing coastal shipping reforms," Mr Hidding said.

"We are the only island state of Australia and we are getting belted through the cabotage arrangements for Australian shipping. It's very material to the success of an international shipping service."

Mr Wilkie and Senator Lambie disagree with Mr Hidding; the two independents are united in their opposition to any change to the cabotage provisions.