The company is informing people by phone and letter

The Steam Packet Company has been forced to alter departure times and in some cases, ports, for some customers because of harbour restrictions.

Bosses have apologised to affected passengers, who are being contacted about the changes by phone and letter.

The TT Centenary festival starts on 26 May and runs until 8 June.

Steam Packet ferries are carrying about 41,000 passengers during the festival, of which 5,000 are affected by the changes.

"Many of these passengers are now being accommodated on our fast craft ferry whereas previously they were booked on our conventional ferry. This will reduce their travel time considerably," the company said in a statement.

We are doing our utmost now to put it right Steam Packet spokeswoman

"The sea traffic in and out of Douglas and UK and Irish ports will be unprecedented over the TT period and all ships will be operating to very tight port slots and turn around times.

"With approximately 18,000 bikes compared with 9,600 bikes booked on our ferries last year and approximately 5,000 cars and vans booked we anticipate an exceptionally busy period.

"The necessary changes have been made to optimise passenger bookings and make this year's Centenary event a successful one for everyone concerned."

A team of staff are currently phoning those with imminent sailings to advise them of the changes.

Those who cannot accept the new arrangements are being offered full refunds, a company spokeswoman said.

"Most people are being understanding and obviously we are reacting quickly to it now," she added.

"We are doing our utmost now to put it right."