Passenger satisfaction levels have dipped below 50% for the majority of train companies, according to a Which? survey of more than 7,000 regular travellers.
For two companies - Greater Anglia and Southeastern - the satisfaction score was only 40%.
South West Trains came near the bottom after only 45% of customers said they were satisfied, according to the study.
Ten of the 19 companies had satisfaction scores of less than 50%, with Merseyrail (70%) the best-performing company.
The survey, conducted among 7,415 UK adults in November 2013 also showed:
- 16% of all passengers experienced a delay on their last journey, with this figure rising to 26% for commuters;
- 21% of commuters said they were likely to have stood on their last journey
- 11% said toilets were not in good working order. This rose to 20% for London Midland , 19% for Southeastern and 17% for First Capital Connect (FCC):
- 11% said they had cause to complain about the last journey they had taken, but 75% did not officially complain. Of those who did complain, more than half (55%) were dissatisfied with how it was handled.
The overall satisfaction scores were based on satisfaction with a company and the likelihood of customers recommending the company. On average, those surveyed had travelled by train 32 times in the previous 12 months.
Which? also asked what passengers felt would improve their journeys and what they would be prepared to pay more for.
Lower ticket prices were top of the wanted list (60%), with 80% saying fares were too high.
People also wanted to see more carriages at peak times (35%), promotions on ticket prices (29%), wi-fi as standard (20%) and improved punctuality and reliability (18% - rising to 29% for commuters only.)
A total of 12% said they want cleaner trains, with FCC and Greater Anglia getting the lowest scores for cleanliness.
However, more than half (53%) said they would not mind paying more if they saw an improvement in service in return.
Half (49%) would pay more for a more reliable service, and a similar number (48%) would pay more to guarantee a seat.
A total of 42% would pay more if the money went towards new trains.
Which? executive director Richard Lloyd said: "It's disappointing to see some train companies consistently falling down on the basics of customer service, with dirty and overcrowded carriages and toilets that don't work.
"Seven rail franchises end in the next two years and we want to see passengers' experiences put right at the heart of the tender process so companies respond to consumer expectations and can be held to account if they don't."
Martin Abrams public transport campaigner for the Campaign for Better Transport, said: ''The Which? survey shows deepening levels of dissatisfaction with many train services.
"Passengers want cheaper, simpler tickets, clean stations and an end to chronic overcrowding.
''We need to learn from franchises like Merseyrail and London Overground which have bucked the national trend.
"These show that investment coupled with a stronger local voice in how services are managed can significantly improve passenger satisfaction. ''
A spokesperson for the South West Trains-Network Rail Alliance said: "We are always pleased to get feedback from our customers to help build on the work we are doing to drive up the quality of rail travel.
"The results of the Which online poll are based on relatively small sample sizes and only cover a fraction of the 210 million passengers who travel with us each year.
"By comparison, independent watchdog Passenger Focus surveys up to eight times as many people a year.
"Last month, this independent passenger survey demonstrated that 81% of passengers were satisfied with South West Trains, with only 5% of passengers expressing dissatisfaction with their service.
"However, we are not complacent and we take into account all passenger feedback as part of our commitment to deliver a better railway for passengers.”
These were the overall satisfaction scores by company:
1. Merseyrail 70%
2. Chiltern 69%
3. c2c 67%
4. Virgin Trains 64%
5. East Coast 59%
6. London Overground 58%
7. ScotRail 56%
8. CrossCountry 52%
9. East Midlands Trains 50%
10= First TransPennine Express 48%
10= Arriva Trains Wales 48%
12. London Midland 47%
13= Southern 46%
13= Northern 46%
15= First Great Western 45%
15= South West Trains 45%
17. First Capital Connect 41%
18= Greater Anglia 40%
18= Southeastern 40%