The Steam Packet is defending its massive fuel surcharge increases, saying the company has absorbed much of the additional costs of global oil price rises over the last few years.
They say since the spring that's involved several million pounds.
The firm has announced a quadrupling of its freight fuel surcharge from £2 per metre to £8, while the passenger surcharge doubles to £5 per single journey, effective from September 1.
The rise has been met with dismay in the Manx carrier sector.
But Director of Harbours, Captain Mike Brew, says the company is not charging its full entitlement under the standing agreement with the Department of Transport.
That was signed between the Packet and the DoT three years ago, permitting rises that reflect the spiralling global fuel price.
The company says the increase will be reviewed in February next year.