Longer ferry crossings between the Isle of Man and the UK as a result of a new Irish Sea wind farm could increase the Steam Packet's fuel bills by around £400,000 per year.
That figure has been given by the infrastructure minister in a letter to the offshore developer Centrica.
David Cretney's told the company any permanent deviations to ferry routes to Liverpool and Heysham are likely to be seen by the Manx government as 'unacceptable'.
And the minister's pointed to UK government marine policy highlighting the 'lifeline' ferry services Island communities rely upon.
In the letter Mr Cretney quotes figures provided by Captain Kane Taha, Marine Manager for the Steam Packet Company.
Based on Centrica's current proposals, permanent shipping deviations to existing routes to the UK would add 5,000 additional miles per year at an estimated cost of £400,000.
Mr Cretney says that could reduce the Steam Packet's ability to achieve the number of trips to the UK, Belfast and Dublin required to meet its contractual obligations.
It could also put at risk the operator's ability to meet the peak in demand during TT.
Last week senior figures from the Packet and Director of Harbours Mike Brew met UK government officials to outline their concerns.
These will be reiterated during a consultation by Centrica on its proposals, due to start soon.