High-speed ferries between Ireland and Britain are slowing down by a quarter of an hour per trip to save fuel and face being replaced by conventional ferries operating at half the speed unless the oil price falls.

Stena Line has also introduced a fuel surcharge of £10 per vehicle and £2 for foot passengers.

The crossing time between Dun Laoghaire, Co Dublin, and Holyhead, North Wales, will rise from 99 minutes to 115. The trip from Belfast to Stranraer will take 119 minutes, an increase of up to 14 minutes depending on the time of day. The reduction in speed will reduce fuel consumption by 8 per cent.

Michael McGrath, Stena’s Irish Sea director, hinted that the high oil price could result in the withdrawal of the HSS ferries, aluminium catamarans the size of a football pitch that travel at more than 40mph.

They would be replaced by conventional ferries operating with a top speed of 25mph, meaning journey times would return to the three hours that was normal before the HSSs were introduced in the mid-1990s.

Mr McGrath said: “As fuel rises, all ferry operators are threatened with major change. Whether the \ have a life or not depends on the customer’s willingness to pay.”

Stena blamed high oil prices last year when it withdrew one HSS from the North Sea route between Harwich and the Hook of Holland. The price then was $70 (£38) a barrel but has since almost doubled. The North Sea HSS is being stored in Belfast awaiting a buyer but, like dozens of fast ferries laid up in docks around the world, may never return to service.

The HSSs were designed in the 1980s when oil was a fraction of its current price and were built to operate until at least 2022. They use more than twice as much fuel as a conventional ferry. They consume gas oil, similar to kerosene used in jet aircraft and double the price of standard marine fuel.

Container ships are also slowing down to save fuel, adding two or three days to the voyage from manufacturing centres in the Far East to European ports.

A study has found that the world’s shipping industry wastes almost three million barrels of oil a day by using ageing vessels that have not been upgraded with fuel-saving technology.

The DK Group found that fitting new propellers and engines and installing devices that allow ships to glide on a cushion of air would reduce global marine fuel consumption by up to 40 per cent.

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