The new ship has 340 cabins and could carry 1,400 passengers
A co-operative aiming to restart the Swansea to Cork ferry says the service will not run until early next year.
It had been hoped a new ship would start regular crossings between Wales and southern Ireland before the summer.
But the board said longer than expected negotiations over a replacement ferry meant many travellers had already made arrangements for this year.
It said after careful consideration it now planned to launch the service on 1 March 2010 - St David's Day.
The Swansea to Cork ferry, which started in 1987, has not run since late 2006 when the ship was sold.
The co-operative has raised over £2.5m from small investors and established a new company called the Fastnet Line.
In a statement, Conor Buckley, chairman of the co-operative, said: "We reluctantly took this decision in the light of the large part of the booking season already lost to the service and the fact that many potential passengers have already made their bookings for the crucial July, August and September sailings.
"We would have liked to have the service resumed for this summer but, despite the enormous amount of work we have already put into the formation of the co-op, we feel that there is an overpowering economic case to not proceed this summer."
He said he realised many people would be disappointed.
"No one would thank us for rushing into service now and sustaining huge losses.
"It would undermine everything we have worked for and would be a potentially huge loss of shareholders money.
"It is far better that we continue with the very solid foundations we are building now and ensure a totally sustainable business for the next 20-plus years. We have to take the long term view."
Backers say since the ferry stopped, economies on both sides of the Irish Sea have suffered.
The consortium has a replacement ship - the Julia, which has 340-cabins.
The rest of the funds for the business have come from bank loans, industry sources and grants.