Doubts over the fairness of the Spirit of Tasmania's pricing structure are being floated by Andrew Wilkie.
In federal parliament's question time, the Clark Independent has requested the government check into allegations the ferry's temporary free passage for vehicles campaign, funded by extra Commonwealth money, is a cynical sham.
"Yes, vehicle charges have dropped, but at the same time it seems TT-Line is jacking up passenger and cabin fares, so it can cost more to sail with a car than it did before the promotion, this would be state sanctioned misuse of federal funding, a rip-off and another blow to the Tasmanian economy and tourism sector."
Deputy Prime Minister Michael McCormack has indicated a willingness to investigate.
"Member for Clark, if you have any specific allegations in relation that you would like to be investigated, I would be very happy to look at them."