Passenger satisfaction with Britain's railways has fallen by two percentage points over the past 12 months, new figures show.
Some 81% of passengers were satisfied with their journeys in autumn last year, according to a survey of more than 29,000 people by watchdog Transport Focus.
This compares with 83% in autumn 2015.
Public transport campaigners claimed the results show that more emphasis should be given to short-term investment projects.
Lianna Etkind, of the Campaign for Better Transport, said: "This survey confirms passengers are paying through the nose for a shoddy service, and the Government appears not to care as long as the money keeps rolling in.
"There is no point spending billions on increasing capacity whilst ignoring smaller scale investment in reliable infrastructure.
"We want to see more line-based infrastructure funding and a fix-it-first approach to rail investment to help tackle the woeful level of service many passengers have to put up with."
The proportion of passengers satisfied with punctuality/reliability dropped from 78% to 73% compared with autumn 2015.
Overall satisfaction declined significantly for Southern (down 12 percentage points to 65%), ScotRail (down seven percentage points to 83%) and Great Northern (down seven percentage points to 78%).
Transport Focus chief executive Anthony Smith said: "The results around the country are disappointing. Scottish passengers and those travelling in peak hours in London and the South East are bearing the brunt of poor performance.
"The timetable on parts of the London and South East's railway can be a work of fiction which passengers cannot rely on. As passenger numbers rise, parts of the rail network will remain brittle until welcome improvements are in place and working."
Analysis by the watchdog found that satisfaction is "significantly lower" for those passengers who travel into London during peak hours.
Punctuality, value for money and dealing with delays for peak-time passengers are particularly low for certain rail firms:
:: Punctuality on Southern - 30%
:: Value for money on Gatwick Express - 12%
:: Dealing with delays on Southern - 12%
Southern passengers have suffered months of disruption because of a row between the company and trade unions over the role of guards and driver-only trains.
Jacqueline Starr, managing director of customer experience at the Rail Delivery Group, representing train operators and Network Rail, said: "We know we must do better.
"We're sorry when customers don't get the service they expect, including those affected by strikes. Everyone in the railway is working hard to make train journeys better from start to finish.
"After decades of under-investment and with passenger numbers soaring to 4.5 million a day on thousands more trains, the railway is full in many places.
"Rail companies are working together to deliver more than £50 billion of improvements, including more than 5,500 new train carriages, to tackle congestion and make journeys faster, more comfortable and more reliable. While we build the bigger, better railway the country needs there will be some disruption."