An MHK has told the Keys the Liverpool Ferry Terminal has so far cost taxpayers more than £100m.
It originally had a price tag of £38m.
In Keys, Lawrie Hooper asked Minister Tim Crookall what the cost would be, Mr Crookall said he could not reveal a figure due to ongoing legal issue.
However, following a warning that he would do it, Mr Hooper used his knowledge of the figures from his time in the DoI to say it had already cost “somewhat north of £100m”.
He added: “Would he [Mr Crookall] also agree that now that the contractual process, as he said, itself, has been closed down, has finished and that the legal dispute that is ongoing actually is about recovery of cost, because that’s the way the contract is structured.
“All the money has already been paid out. So the reality is now we are working back from a theoretical maximum cost backwards towards what the actual final settlement will be.”
Mr Crookall would not confirm that figure but said negotiations would carry on for up to another 18 months with Tynwald having to provide a supplementary vote to top up its budget.