The company is informing people by phone and letter

The Steam Packet Company has altered departure times and ports for several sailings, leaving passengers confused and, in some cases, stranded.

Operations director Mark Woodward said customers were told that bookings were provisional, but accepted that the situation was "not ideal".

"We apologise to those passengers affected," he said.

About 50 TT riders, team members and their trailers were refused travel on Wednesday's sailing from Heysham, Lancashire.

Other disgruntled customers have contacted local media to complain about the last-minute alterations.

The Steam Packet company is operating more than 360 sailings during the TT Centenary Festival because of high demand, forcing it to use chartered vessels and additional port slots.

We are aware that the situation is not ideal and would of course prefer to offer a higher degree of certainty to our customers Mark Woodward, Steam Packet Company

Mr Woodward said many companies had been reluctant to commit to a short charter during the TT period.

"Without these firm guarantees we can only offer provisional vessels and timings for the following year's TT to some of our customers," said Mr Woodward.

"For precisely these reasons, we have had to alter some of those provisionally booked sailings this year.

"We are aware that the situation is not ideal and would of course prefer to offer a higher degree of certainty to our customers."

Mr Woodward said the company would look at other options for the future.

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.