Public trust in nearly all rail operators has decreased, linked to passenger dissatisfaction over punctuality and reliability.
The only rail firm that saw trust improve was Southern. However, it remains the lowest-ranked operator, analysis from Transport Focus suggests.
Southern-owner Govia Thameslink said its services were improving.
Transport Focus, an independent watchdog, analysed passengers' opinions between spring 2017 and autumn 2018.
The Department for Transport said it was conducting a review which would address concerns raised by passengers.
Over the survey period, trust declined in all rail operators apart from Southern.
However, in terms of trust, Southern was still bottom of the pile, with only 22% of passengers saying they trusted the firm last autumn.
Two other Govia Thameslink firms were among the worst performers, Thameslink and Great Northern, which had trust ratings of 27% and 24%.
Transport Focus said there was a link between levels of customer trust and the punctuality and reliability of services.
Throughout 2016, Southern was , with tens of thousands of services fully or partly cancelled.
And in 2018, paralysed large swathes of the UK's rail network.
A Govia Thameslink spokesman said Southern had been affected by industrial action, while Thameslink and Great Northern had been hit by timetabling issues.
"This report reflects the industry-wide issues surrounding the timetable changes last May," the spokesman said.
"Passengers have been paid £17m in additional industry compensation and we are now consulting the communities most affected on how we should invest a £15m fund dedicated to improving their journeys."
The spokesman added that both punctuality and reliability had improved since the autumn.
The rail firm which lost the most trust over that period was South Western Railway. In autumn last year, 27% of people said they trusted the firm, compared with 47% in spring 2017.
A South Western Railway spokesperson said: "We know that customer trust is heavily linked to train service punctuality. Unfortunately, the periods covered in the survey include some major infrastructure challenges and also industrial action which would have had an impact on our performance.
"We are working very closely with our colleagues at Network Rail to improve performance for our customers and we're pleased that we're starting to see positive results."
The two train operators with the highest trust ratings were Grand Central and Heathrow Express, which both consistently had scores above 70%.
Transport Focus chief executive Anthony Smith said: "There are some wide variations between train operators that keenly reflect the passenger experience.
"Public trust in the railway is fragile but has never been more important. Building a good relationship with passengers will need to be a central part of any reform programme for the railway.
"Even small delays can damage passenger trust, so punctual services and accurate information are essential."
All change please
The watchdog produced its report to feed into the Williams Rail Review, which is looking at how to improve of the state of the railways.
A Department for Transport spokesperson said submissions to the review would be "crucial to our recommendations for reform".
"The review is focused on reforms that will put passengers first, provide value for taxpayers and deliver economic, social and environmental benefits across Britain," it said.
In December last year, Keith Williams, who is leading the review, .
However, Transport Minister Chris Grayling is not in favour of renationalisation, having said he preferred the review to "more effectively balance public and private sector investment".