The Government believes that the romantically named Night Riviera sleeper service, from Paddington to Penzance, no longer represents value for taxpayers’ money. It loses about £1 million a year, despite being fully booked on many nights.

The Scottish sleepers, from London Euston to Edinburgh, Glasgow, Inverness, Aberdeen and Fort William, are also under threat. The rail regulator is investigating the costs of all loss-making rail services and the sleepers are considered the least likely to make a profit.

A daytime intercity train carries up to 500 people while a sleeper has as few as 100 berths and requires twice as many on-board staff. The special rolling stock is also used for only about eight hours a day, compared with 18 hours for normal trains.

The Scottish sleepers lose much more than the Cornish service. First ScotRail, the operator, will not reveal how much the Scottish sleepers cost the taxpayer, but two years ago they were reported to be losing £20 million a year.

A previous attempt to close the Fort William service was defeated in 1995 after a legal battle and a fierce campaign by politicians and Scottish lairds and landowners.

The immediate threat, however, is to the Cornish service, which could be scrapped next April when a new company takes over the franchise.

The Strategic Rail Authority has ordered all those bidding for the franchise to give a separate estimate of the costs of running the sleepers. In a statement it said it was “keen to build an accurate picture of the cost of running these services”. It was “concerned (they) may not represent good value for money because of low passenger demand”.

A Whitehall source said the Cornish sleeper was being targeted first because it was less politically sensitive. The Liberal Democrats won every Cornish seat in the last election. By contrast, the Scottish sleepers are popular among Labour MPs and ministers returning to their constituencies north of the Border.

Julia Goldsworthy, the Lib Dem MP for Falmouth and Camborne, said that Cornwall was already England’s poorest county and the loss of the sleeper would inflict further damage on the economy.

“The sleeper is very important to local businesses because it’s the only way to get to London for an early meeting,” she said. “People forget that England is as wide as it is long. Unlike Scotland, we don’t have frequent air services to London.”

Malcolm Bell, the chief executive of SouthWest Tourism, said: “In numerical terms only a fraction of visitors use the sleeper. But it’s a very important selling point because we can say to people that they don’t need to waste a day getting to Cornwall. They can arrive fresh in the morning in the middle of Penzance.”

But the few rail companies that do not receive a subsidy are increasingly resentful at having to help to prop up loss-making sleeper services.

James Sherwood, the president of Sea Containers, which owns GNER, has called for sleepers to be shunted to the scrapyard. “We run fast, early morning trains which get people to London when they need to be there,” he said. “But the authorities insist on running sleeper services. The taxpayer is paying the hotel bills of the people on those trains.”

FIVE SERVICES YOU CAN STILL STAY AWAKE FOR

The Blue Train, South Africa
27-hour trip from Pretoria to Cape Town, with up to three return services a week. Passes by gold mines and the parched interior of the Karoo, while the 80 passengers on board are served by 30 staff. Cost of berth: 12,680 rands (£1,035)

The Canadian, Canada
Three-night journey from Toronto to Vancouver through the Rockies. The current trains, built in the 1950s and restored 20 years ago, have up to 25 carriages, complete with domed viewing coaches and lounge cars. Cost: up to Can $2,000 (£875)

The Ghan, Australia
At least once a week, the Ghan (named after Afghan camel traders who plied their trade in the Northern Territory) trundles for 47 hours across the harsh interior from Darwin to Alice Springs, on to Adelaide and back again. Cost: from A$1,830 (£766) in Gold Kangaroo class

The Venice Simplon-Orient-Express
More than 14,000 passengers each year make the four-day journey from London to Venice in vintage Pullman carriages. Boarding at Victoria, you have 24-hour butler service and access to the extensive menu in the dining car. Cost: from £2,390

The Trans-Siberian Railway, Russia
It takes seven days to get to Vladivostok from Moscow, but it would be a shame if you did not stop off to enjoy the sights, such as Lake Baikal, the largest freshwater lake. Accommodation is a small four-berth cabin, sharing with anyone from a Mongolian to an Aussie backpacker. Cost: from £609

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