British rolling stock is now 21 years old on average
The average age of trains on Britain's railways is the oldest in at least 15 years, an investigation has found.
A think-tank claimed passengers are "paying through the nose for decrepit trains" while public transport campaigners said there is a "postcode lottery" for train quality.
Rolling stock is now 21 years old on average, Office of Rail and Road (ORR) statistics show.
Press Association analysis found this figure is higher than at any point in publicly available records.
The ORR said older trains can result in less comfortable journeys, poorer reliability and worse performance than modern versions, although it also noted that older rolling stock can be refurbished.
Travellers using the Caledonian Sleeper service between London and Scotland are provided with Britain's oldest trains on average, at 41 years.
Merseyrail, which runs trains in Merseyside, has the second oldest fleet at 37 years.
Both operators plan to introduce new rolling stock in the coming years.
TransPennine Express trains, running between cities and major towns in northern England and Scotland, are the newest in Britain at just nine years old on average.
Trains in London and south-east England are typically 19 years old, while "regional services" are 24 years old.
The latest ORR figures cover the period between January and March 2016, with records going back to July 2000.
Ed Cox, director of think-tank IPPR North, said: " It is little wonder that Britain lags behind other developed nations when commuters pay through the nose for decrepit trains.
"Northerners in particular will be familiar with Pacer trains which leak whenever it gets wet. This is a national disgrace and just not what you'd see in Germany, France or Japan, or even down south."
Rail fares increase by an average of 2.3% across Britain from Monday.
Mr Cox added: "To make journeys cheaper, cleaner and greener, areas outside the capital must be given Transport for London-style powers to raise money to invest in transport and take back control over spending decisions."
The Rail Delivery Group, representing train companies, said it expects the average age of Britain's trains to drop to 16 years by 2019 due to the introduction of more than 4,500 new carriages with a capital cost in excess of £7.5 billion.
Lianna Etkind, public transport campaigner at the Campaign for Better Transport, said the current age of trains "exemplifies the lack of public and passenger involvement" in the network.
She went on: "More people than ever rely on the railways, they contribute a bigger percentage to running costs than ever, they pay more for their tickets than ever, and yet there is a postcode lottery in the kind of trains they are served by.
"We need a strategy from the Government which involves passengers and the wider public in decision making, makes clear what their future plans are on things like electrification and clarifies the roles of the rolling stock companies, the train operators and the Government in paying for updated rolling stock."
Last month public spending watchdog the National Audit Office warned that delays in electrification of the Great Western rail line could mean passengers in the North and West of England may have to wait longer for newer trains as the reallocation of rolling stock is held up.
Railway historian and writer Christian Wolmar said investment in new trains in Britain is "very lumpy" because it " isn't properly planned and we don't really have a principal domestic supplier".
He added: "I f we had a sensible process we would have a steady, smooth production line that we operate all year round, producing rolling stock at regular intervals.
"The whole thing would be rational and much cheaper."
A Department for Transport spokesman said: "We are delivering the biggest rail modernisation programme for over a century and will be rolling out more than 5,000 carriages over the next four years which offer more seats, wi-fi and air conditioning.
"South West Trains will start testing the first of 150 new carriages in the new year and the first new trains on the Great Western mainline will begin operating next summer, before they are brought in on the East Coast route.
"Through rail franchising, we also expect the rail industry to come up with more proposals to introduce new carriages and improve services."