Could there be anything less ghostly than the scene at London's Paddington station on this bright December morning? The sun is sparkling through the glass of the newly restored canopy of Brunel's magnificent terminus as commuters and shoppers scurry across the concourse, cheered by the prospect of Christmas.

Yet, waiting for me on Platform 14, in one of the darkest, dankest, greasiest and most inaccessible corners of the station, is one of the spookiest trains in Britain: the 11.36 "ghost train" to Gerrards Cross in Buckinghamshire.

The Gerrards Cross ghost train is one of several ethereal services that wend their eerie way around Britain's rail network, almost unknown to the public and running mostly empty, since they operate at deliberately inconvenient times – often offering their passengers no prospect of getting home again.

Yet these zombie services have a very real existence in the minds of the bureaucrats who control our rail system, since they help to maintain a fiction that a railway line is still open, when it has effectively been abandoned.

For the price of an occasional train service with a clapped-out diesel, or in some cases even a bus, the train operators are able to duck the long and costly consultation, accompanied by inevitable howls of public protest, that the law stipulates when a railway line is to be closed. For these reasons the ghost trains are sometimes known as "parliamentary trains".

In this Alice-in-Wonderland world, it is especially desirable that the staff refuse to sell you a ticket. "You're at the wrong station, mate," the man in the booking office tells me when I try to buy a one-way ticket. "You need to take a Tube to Marylebone. That's where the Gerrards Cross trains go from." When I argue, he raises his eyebrows wearily and takes a long swig from a mug of tea. It's only when I refuse to budge, and after some consultation of dusty ring-binders, that a ticket is finally produced. I appear to be the only passenger on board, outnumbered by the driver and the guard – and there's a definite chill in the carriage. Is there a fault in the heating system, or are diabolical powers at work?

One thing I know for certain, having pored over the small print of the timetable, is that there is no train back. I also know that the real diabolical forces emanate not from the supernatural, but more prosaically from mandarins at the Department for Transport who keep the ghost trains permanently suspended in purgatory for their own dastardly purposes.

"You are our only customer today", announces the conductor, Mohammed, inspecting my ticket as though I were being awarded some kind of honour. "Most days we have no passengers at all. But we run this train every day so that Network Rail won't shut down the line. If we stop running this train, then that's it. Kaput."

Certainly, this once mighty main line to Birmingham and Birkenhead, pride of the Great Western Railway until it was downgraded during the Beeching cuts of the 1960s, seems on its last legs. The train crunches along a rusted single track past the back end of the industrial estates off the Great West Road. Here are the bulldozed remains of the Old Oak Common engine sheds that housed the Kings and Castles, among the greatest steam locomotives built in Britain's industrial heyday.

There's another sign of post-industrial nostalgia as we pass behind the old art deco Hoover factory, now a Tesco supermarket. Disused sidings are shrouded in dying buddleia as we pass an old-fashioned wooden signal box and even more antiquated semaphore signals sited incongruously near a gigantic modern waste transfer station.

When I get off at Gerrards Cross, I find I am no longer alone. The ethereal figure at the end of the deserted platform, pointing a camera at the front of the train, is not the Ghost of Railways Past but Dave, an off-duty train driver, who is one of the "ghosties" – rail enthusiasts who travel the land "copping" [spotting] the "parliamentary" trains.

"Actually," he tells me, "they use this route for crew-training in case Marylebone is shut and trains are diverted." He explains that the "parly" trains originated in the Railway Act of 1844, which brought in a maximum third-class fare of a penny a mile and higher safety standards after some stonemasons were catapulted to their deaths from an overturned third-class carriage. The train companies came up with a ruse to duck their responsibilities while sticking to the letter of the law. They would run one decent train a day, often at the worst times and with the surliest staff to put off all but the most determined of passengers. Today's "parly" trains operate on a similar principle, but they are often so packed with "ghosties" like Dave that they defeat their purpose – none more so than the Stalybridge Flyer. This two-coach diesel railcar is one of the rarest trains in Britain, leaving Stockport at 9.22am, on Fridays only, for the short journey around south Manchester. There is no return service, which may be just as well, since many of the "ghosties" who pack the services each week find themselves waylaid at Stalybridge by the legendary real ales and homemade black puddings at Britain's most famous railway buffet. An even rarer service runs between Frodsham and Runcorn, which has only one train a week – on Saturdays in summer.

For many "ghosties", the North of England offers ghost train paradise – or hell if you are one of the few passengers dependent on them. There are only four services a day between Helsby and Ellesmere Port in Cheshire. And at Styal, between Crewe and Manchester, just three services a day stop. (This appears to be true lunacy, since local campaigners have proved that a stop would not add to overall train times.)

Poor Teesside Airport station, on the Darlington to Middlesbrough line, has an average of one passenger a week, making even the most obscure Ryanair Baltic destination appear like Heathrow.

But the most surreal and inaccessible ghost stations of all lie, paradoxically, on Britain's busiest railway, the West Coast Main Line between Euston and Glasgow. Each day the weed-covered platforms at Polesworth in Warwickshire and Norton Bridge near Stafford can be glimpsed tantalisingly by thousands of passengers.

Polesworth, which had six weekday services as recently as the 1980s, now has one – the 07.26 to Crewe. Passengers cannot travel southbound, because the footbridge to the up platform was removed six years ago and no one bothered to put it back. Norton Bridge is in even worse shape. Although it has a nameboard and appears in the National Rail Timetable, it has not been served since 2004, when the footbridge was taken down. Passengers seeking to access what must be one of the most godforsaken stations in the land have to get there on a bus that trundles round the back roads of north Staffordshire. (Though it offers special spooky charms of its own, since the platform lamps are said to light up from time to time spontaneously and inexplicably.)

"The whole situation is completely crazy," says Britain's foremost timetable expert, Barry Doe, of Rail magazine. So why don't the authorities put these sad railway wraiths out of their misery? The problem, Doe says, is that in the old days British Railways were happy to put forward a closure proposal. But since privatisation, the railways have been controlled by the Department for Transport, which is a bit too close to government for anyone to dare raising the politically sensitive subject of axing trains. "We're stuck in a limbo world," says Doe.

When I arrive back at Paddington, after a return journey via Wembley and a hike along the Marylebone Road, the early evening commuters are already besieging the homebound services on what are, according to the latest statistics, the most overcrowded trains in Britain. Here is a subject worth pondering. Is it a quant and charming eccentricity that an empty ghost train leaves the station each day while passengers on others are transported like cattle? Or does it simply confirm that the way we run our railways is totally barmy?