The rate of rail passenger complaints jumped by 7.5% over the past year, new figures show.
Delays and cancellations in London and south-east England drove the increase, according to the Office of Rail and Road (ORR).
Some 29.4 complaints were made per 100,000 journeys on franchised operators in 2016/17, representing a total of 540,000 disgruntled passengers.
Alex Hayman, managing director of public markets at consumer group Which?, said: "It is staggering that more than half a million complaints have been made by rail passengers in the last year alone and shows how badly the sector is failing its passengers.
"We've heard from thousands of people who have to face delays, cancellations or overcrowded trains on a daily basis.
"We need to see the rail regulator given stronger powers so that it can effectively stand up for passengers when rail services fail to deliver.
"The Government must also press forward on its plans to introduce a rail ombudsman."
Jo Causon, chief executive of the Institute of Customer Service, said: "A major factor of rail customer satisfaction is service reliability, but our research identifies staff attitude and behaviour as essential drivers too.
"Customers are more concerned today about staff attitudes and behaviour than they were even five years ago and developing these skills is an essential part of improving customer service."
Punctuality on trains during the past year was the worst since 2005/06, with 12.3% of trains failing to reach their destination within five minutes for commuter services or 10 minutes for long distance trips.
The latest survey of almost 30,000 passengers by Transport Focus in autumn last year revealed that just 81% were satisfied with the railways, a figure which has not been lower since spring 2007.
Five operators in London and the South East, Greater Anglia, c2c, Govia Thameslink Railway, Southeastern and South West Trains, were responsible for 46% of all complaints in 2016/17, compared with 32% during the previous 12 months.
A spokesman for the Rail Delivery Group, representing train operators and Network Rail, said: "We know that the last year has been difficult for passengers on some parts of the railway, and the figures reflect that, but on other parts rail companies working together have raised punctuality to record highs.
"The long-term trend is of falling complaints from customers and our £50 billion-plus upgrade plan is making journeys better."
Great railway journeys
Great railway journeys
Reaching heights of 3000 feet and going 100 miles the other side of the Arctic circle, this trip links Stockholm and Kiruna, in Norway. Highlights include the longest fjord in the world, Sognefjord, which is 126 miles long and 4000 feet deep. Come in the summer, and you'll experience the meaning of the term, 'land of the midnight sun'. Visit greatrail.com for more info.
There's no doubt that this is the most luxurious way to cross India. A steam engine drags the train out of Delhi for a week-long trip to the royal estate at Rajasthan. Along the way there's canoodling with elephants in the pink city, Jaipur, a camel safari in the desert at Jaisalmer and a tour of Agra's extraordinary Taj Mahal. Visit thepalaceonwheels.net for more.
Beginning in Cuzco (one of South America's most enchanting cities) and winding its way along the path of the Urubamba River, Peru's famous railway line takes in colossal Andean mountains, Inca ruins and llamas galore. And that's before you get to the unbelievable lost city of Macchu Picchu. For more info, visit machupicchutrain.com for info.
Great Rail Journeys offers berths on arguably the greatest passenger train on the planet, the Golden Eagle, for an astounding ride covering 11 time zones. This epic journey begins in Warsaw and ends 8,000 miles away in Vladivostock. Along the way there's a chance to go ice fishing in the world's biggest lake, Baikal, take a troika carriage in Suzdal, lunch out in a traditional Mongolian 'yurt' tent and gape at the golden domes of Yaketerinburg.
The Orient Express is a byword for luxury travel. Traditionally it served Paris and Istanbul, but that's no longer the case. These days it runs between Strasbourg and Vienna, so you'll have to improvise. Four journeys- Paris-Strasbourg, Strasbourg-Vienna, Vienna-Belgrade and Belgrade-Istanbul- will suffice, taking you from the heartland of Western Europe to the gateway of Asia. Truly a journey worth undertaking, 127 years since its maiden passage.
This railway has been in operation since 1893, giving spectacular views of one of Switzerland's most beautiful regions. It climbs from Interlaken to a height of 11332 feet at Jangfraujoch Station. A phenomenal feat of engineering allows the train to enter through the middle of Eiger mountain. From the top you can see as far as the Black Forest in Germany- this is the so-called 'Roof of Europe' after all. Inside the glacier is Ice Palace, an exhibition of ice sculptures. The cost of a return fare is steep - fares are over hundred quid - but well worth it. Visit jungfrau.ch for more.
The Blue Train offers a luxury service crossing South Africa. It takes in Victoria Falls, the haunting barren landscape of the Great Karoo and the incredibly seaside city of Cape Town. And along the way you'll be glued to the window hoping to spot elephants, lions and other wonderful animals in their wild habitat. Visit bluetrain.co/za for more.
If you want a taste of real speed try a ride on Japan's Shinkansens. The latest model of these bullet trains reaches speeds of 186mph. This means you reach Osaka from Tokyo (515 km away) in a mind-boggling two hours and 25 minutes. You can take a Shinkansen all the way across Japan, from Kagoshima in the south-west to Hachinoche in the north-east. Just be sure not to blink. Visit seat61/japan for more.
Beginning in Tangier (the sleazy port which inspired the likes of Paul Bowles, William H. Burroughs and Jack Kerouac) the train stops at the delightful medieval town of Asilah . Then it heads inland from the modern metropolis of Casablanca, home to the stupendous Hassan II Mosque. The closer to Marrakech one gets, the land becomes pinker and barer, until the foothills of the Atlas Mountains- where the magnificent city itself appears in all its glorious weirdness. Visit greatrail.com for more.
This engineering triumph – which cost $90 million and took 90 years to complete – crosses the guava-spotted deserts and canyons of northern Mexico, linking the Pacific Coast and Chihuahua City by way of 87 tunnels and 36 bridges. The Copper Canyon itself features two climactic zones, so sub-tropical forests give way to a cool alpine climate with oaks and pines. for Visit mexicoscoppercanyon.com for more info.
Don't listen to what anyone else says; from Switzerland to Siberia, by bullet train or steam engine, it's still the best way to travel.