The number of rail passengers satisfied with their journey is "significantly down" compared with a year ago, according to a new study.

A huge survey of 27,000 passengers found that 81% expressed satisfaction with their journey when questioned last autumn, 2% down on the previous autumn.

The study, by watchdog Passenger Focus, did not include the Christmas period.

Passengers have also suffered delays and cancellations in Sussex since the start of this year because of signalling and other problems.

Satisfaction levels varied between 74% and 94% for different train companies, with the highest-scoring operators Heathrow Express and Grand Central, (both 94%) and Chiltern (93%).

However all of the lowest-scored were train companies which operate in Sussex. Govia Thameslink and Southern both scored 77% and Southeastern (74%).

Southeastern's overall satisfaction score fell 11% compared to a year ago, while Cross Country's dropped 4% in a year.

Anthony Smith, chief executive of Passenger Focus, said: "Rail passengers' satisfaction is driven by getting trains on time. Many are being let down - fare increases, billions in Government investment and promises of improvement don't seem to be delivering change on the ground.

"The high-profile disruption after Christmas and at London Bridge will only have added to the gloom.

"Passengers do not care who is to blame for things going wrong and for some of them the timetable is a work of fiction. If it really is the case that better day-to-day performance can't be achieved, then an honest, open debate is now needed so that passengers might be able to trust the promises made by the industry again."

The number of passengers who believed their trains were punctual and reliable also fell by 2%, to 77%.

The only areas where satisfaction improved were shops, eating and drinking facilities and other services at railway stations.

There was a decline in other areas monitored, including train speed and enough room to sit down or stand on a train.

Fewer than half of passengers believed fares offered value for money, similar to the previous year.

In London and the South East, there were declines in satisfaction with the helpfulness and attitude of staff as well as how train companies dealt with delays.

Only three out of four passengers in London and the South East were satisfied with punctuality.

Manuel Cortes, leader of the Transport Salaried Staffs Association, said: "It is hardly surprising that passenger satisfaction is falling when commuters are paying record high fares for a worsening service.

"Southern and Southeastern are the worst offenders in delays and cancellations. When you look at real-time delays, barely one in two trains on time.

"And for this, many passengers are paying £4,000 and £5,000 for an annual season ticket. It is an absolute disgrace."

Michael Roberts, director general of the Rail Delivery Group, representing rail operators and Network Rail, said: "These results show how passenger satisfaction has been dipping after years of steady improvement and they reinforce our determination to do better.

"The timetable is our promise to passengers, and too often we aren't making good on this commitment. To improve, we are working closer together as an industry to deliver better reliability so that more people can complete their journeys on time and improve information to passengers, particularly during disruption."

Rail Maritime and Transport union general secretary Mick Cash said: "This report throws up yet more evidence that two decades of privatisation, fragmentation and under-investment on Britain's railways have left passengers angry and frustrated as they see the hard cash they pay over for extortionate fares drained away in profits to the train operating companies.

"It is telling that satisfaction on the commuter routes into London, where there is a drive on to axe guards and station staff in the name of profit, is in free-fall and that should be enough to force these companies, like the new operators on Thameslink, Southern and Great Northern, to abandon their cuts plans.

"It defies belief that constantly-failing train companies are allowed to hang on to their money-spinning franchises while passenger anger reaches boiling point. The only solution is to end the 20 years of private racketeering and return the whole railway to public ownership."

Passengers on long-distance trains were more satisfied, at 86%, although this was also down by 2% compared with a year earlier.

They were happier with ticket-buying facilities, shops and other services although less satisfied with the upkeep and cleanliness of trains and punctuality.

There were wide variations within individual routes with passenger satisfaction over value for money (from 29% to 86%), punctuality (56% to 98%) and enough room on trains (43% to 95%).

For regional train companies, 84% of passengers were very or fairly satisfied with their journey, unchanged from a year earlier.

David Statham, managing director for Southeastern, said: "These disappointing scores show just how important a reliable and punctual service is to passengers. We're committed to improving performance through a robust new timetable, which has seen punctuality improve over the last two to three weeks; and a programme of investment in our trains. We're also working together with Network Rail to identify the areas for their multi-million pound investment scheme to target to deliver the greatest benefit to passengers.

"We recognise that we have a lot more work to do to ensure that our passengers are more satisfied with the service that we provide. My senior team and I have been out and about around our network seeing first-hand how our service operates and listening to passengers' concerns.

"Over the next three years we're investing more than £70 million in the things that our passengers tell us are important to them. This investment will enable us to provide better information to our passengers, improve the interior and cleanliness of our trains, refresh the look of our stations and provide extra staff to deliver more face-to-face customer service. Passengers will start to see the results of this investment over the next couple of months and we hope that this will be reflected in the results of the next passenger survey, which is already under way."

Rail Minister Claire Perry said: "We are investing record amounts of money in our railways to improve journeys for passengers. But this welcome long-term investment has to be made in a way that does not mean unacceptable delays for passengers travelling today.

"These statistics show that Network Rail and many train operators have to work together to improve reliability and communications around delays. I want passengers to see and feel the benefits of this huge investment as soon as possible."

Shadow transport secretary Michael Dugher said: "This demonstrates once again that under David Cameron rail passengers are being let down and ripped off, and it shows that things have got worse on our railways.

"Since 2010, overall passenger satisfaction with their journey is down, the percentage of passengers satisfied with punctuality is down and the percentage of passengers satisfied with value for money is also down. Across the board, passengers are saying the service they receive is getting worse.

"At the same time, people have been hit with massive fare rises of over 20% since 2010.

"David Cameron's approach of just sitting back and doing nothing to reform the railways is not an option. Labour will act on fares, plus deliver a better deal for passengers and taxpayers by making big changes to the railways, including giving passengers a real voice for the first time."

John Larkinson, of the Office of Rail Regulation, said: "We know that how the rail industry deals with delays is a big cause of passenger dissatisfaction.

"So we remain concerned that a quarter of passengers are still unhappy about this, despite recent initiatives to improve information during disruption.

"This demonstrates the importance of the industry delivering further improvements faster, so passengers get accurate and timely information if trains are delayed."