Earlier this month, the Coalition government reaffirmed its promise to provide $400 million over 10 years for work on the 160-kilometre stretch connecting Launceston and Hobart with the first funds to flow next financial year.

Tasmania's peak motoring body, the RACT, has written to the major parties calling on them to commit to chipping in the state's fair share of the national highway project, which is usually 20 per cent of the total cost.

RACT public policy manager Vince Taskunas urged the next state government include in its first budget a spending requirement of up to $100 million over 10 years on the Midland Highway.

The state government signed a memorandum of understanding with the former federal Labor government that had committed $500 million over 10 years, agreeing to chip in its 20 per cent share, but the expenditure was not reflected in the state budget because the details were yet to be finalised.

A spokesman for Tasmanian Infrastructure Minister David O'Byrne confirmed Labor intended to make the same commitment in relation to the new Coalition government's Midland Highway plans but had not yet been approached to finalise the deal.

The federal Assistant Minister for Infrastructure Jamie Briggs' office could not be contacted yesterday but Mr Taskunas said Mr Briggs had told the RACT at a meeting this month that he expected the state to fund the 20 per cent as usual.

However, Tasmanian Liberals infrastructure spokesman Rene Hidding said state funds were not necessary.

"The federal contribution to the Midland Highway is not contingent on state funding," Mr Hidding said.

"The first $40 million of the $400 million will be in the coming budget. We will consider state- based contributions to the road upgrade in the context of future budgets."