In November Tasmanian Attorney-General Guy Barnett wrote to his federal counterpart Mark Dreyfus issuing a February deadline for the Commonwealth to commit to providing the funds.

The money would, broadly speaking, be spent on including a fifth courtroom in the plans for a new Burnie courthouse.

The state has committed $86.5 million towards that four-court complex to house the region's Supreme and Magistrates' courts.

The fifth court would be a dedicated venue for the North-West circuits of the Federal Circuit and Family Court of Australia (FCFCOA), which has been housed at various locations including the Burnie Arts and Function Centre and recently the existing Supreme Court.

However, in a letter to Mr Barnett, Mr Dreyfus has asked for further clarity around a number of issues he says the Commonwealth is currently unclear about.

Mr Dreyfus has asked for clarity about how the state arrived at the $15 million figure, and what specifically that money would secure for the FCFCOA, as well as details about projected cost escalations given the lengthy timeframe associated with the project.

Mr Barnett said he welcomed "recent discussions with Mr Dreyfus about a way forward to secure a permanent home" for the FCFCOA's North-West circuits.

The state took ownership of the site on the corner of Wilson and Ladbrooke streets in Burnie where it intends to build the new courthouse at the end of last year, but no further detail on a firm design and construction timeframe has been provided.

Mr Barnett said design work will begin as soon as an architect is appointed, but that "it is critical a decision is made quickly" about whether they will design a building with more than the planned four courtrooms.

"Due to the demand on the state courts, there is no capacity to use these courts for Federal Court and Family Court of Australia hearings," Mr Barnett said.

Mr Dreyfus has supported ensuring the FCFCOA has a permanent home in the North-West in the past.

"It is not in the interests of either the Tasmanian or Commonwealth governments for the people of North-West Tasmania to not have proximate access to the FCFCOA," he said.