Renationalising the railways does not go far enough – Labour should spur a rail renaissance by allowing people around the UK unlimited train travel for a flat fee, campaigners have said.

Under a “climate card” system, passengers could pay a simple subscription to gain access to train travel across all services. This could be effective if set at £49 a month, according to research published on Thursday, though travellers on fast long-distance trains and those on routes in and through London would need to pay a top-up to reflect the greater demand on those services.

If such a system were implemented across the UK, it would be likely to result in a loss of revenues to the railways of between £45m and £637m, depending on the uptake, the report found. This would have to be subsidised by the government, but transport is already subsidised in various less effective forms, and the report found the climate card would generate economic growth and improvements to health from lower air pollution.

Introducing a flat fare in this way would have the benefit of bypassing the UK’s byzantine system of fare structures, in which potential fares currently number about 50m, and would make life easier for both season ticket holders who travel frequently by the same routes, and less frequent travellers who take a variety of journeys.

Greenpeace, which commissioned the study from the non-profit transport thinktank Greengauge 21, said a climate card would attract many more passengers to the railways and reduce car journeys, cutting greenhouse gas emissions and air pollution. Transport accounts for a stubbornly high proportion of the UK’s total carbon emissions, in part because of a lack of public transport in many areas outside London, and the rapid rise in sales of heavier cars including SUVs.

The savings to rail users could be substantial. Season ticket holders for Stoke-on-Trent to Manchester pay £379 a month, according to additional research by Greenpeace; season tickets between Liverpool Lime Street and Manchester Piccadilly or Victoria cost £260 a month; between Leeds and York the price is £278 a month. Cars on average cost £319 a month to run, and fuel duty has been frozen repeatedly at a cost of £9bn a year in tax revenues, according to the Institute for Fiscal Studies.

The report, entitled Fare Britannia, published on Thursday, estimated that a climate card covering all the UK nations could generate an additional 122m rail trips a year, which would save 40m car journeys and reduce emissions by about 380,000 tonnes of carbon.

The climate card would not be compulsory, and other train fares would still be available, but if the experience of other countries is anything to go by, such a scheme would probably prove popular with users.

Paul Morozzo, a senior transport campaigner at Greenpeace UK, said: “Our current rail fare system is far too complicated, confusing and expensive – it’s time to redesign it with passengers in mind. A monthly climate card would simplify the ticketing system, save commuters hundreds of pounds a month and cut emissions – a triple win.”

The report suggested that the card should be tried out in the north of England first, which would help rebalance the economy and reflect the fact that spending on transport in London is £864 a year compared with £349 in the north.

Jim Steer, the director of Greengauge 21, said: “We suggest it would be best to start in the English regions away from the south-east – which dominates the nation’s rail use currently. The next step could be for the newly fashioned Great British Railways to be given the task of looking into a climate card as a way of boosting regional economies within the timescale of this parliament.”

Other countries have introduced similar schemes, which have tended to be popular, but have shown significant costs to the public purse. Germany introduced a flat fare of €9 a month during the recovery from the Covid-19 pandemic in 2022, to encourage people back on to public transport. Though it was widely popular, this cost the government at least €2.5bn, which attracted criticism. The ticket was later replaced by a €49 monthly rail pass, which is still in operation, with a €1.5bn a year government subsidy.

The National Infrastructure Commission has highlighted that poor public transport in UK regions acts as a brake on economic growth. Attracting people to the railways could bring economic and productivity benefits in return for public investment, the report’s authors argue.

A DfT spokesperson said: “This government is committed to encouraging greener ways to travel and improving the state of public transport.

“That’s why we’re empowering local leaders to deliver better bus services, overhauling our railways to put passengers first and simplifying ticketing to deliver better value for money when taking the train.”