Taking the train to holiday spots in Europe is four times more expensive than flying on average, according to new research.
The study from Greenpeace UK, published as schools break up for summer holidays, compared ticket prices on more than 100 routes between major European cities.
It found that people wishing to travel in a more environmentally friendly would pay roughly twice the amount than if they flew.
But the cost rises to four times as much for journeys to or from the UK, because the train connection is so costly.
Dr Doug Parr, Greenpeace UK’s director of policy, blamed it on the “twisted economics of the transport industry” that taxes train companies more than airlines.
It comes as a heatwave, fuelled by climate change, affects many popular tourist destinations in Europe.
Aviation is responsible for about 2.5% of global carbon dioxide emissions, but not many people fly – only about one in 10 of the world’s population takes a flight each year.
The researchers analysed routes between large cities in 27 countries, and checked the prices on nine different dates ranging from four months in advance to just a few of days before departure, to factor in price changes and last-minute deals.
Flights were cheaper on 79 out of 112 routes – about 70%.
The price difference was more dramatic on specific routes such as travelling from Barcelona to London.
By train, the journey was 10 times more expensive on average, and up to 30 times at short notice – the biggest price difference in this analysis.
London to Barcelona takes about 10 hours by train and two hours by plane, although flying involves extra time to check in time and travel into the city centre on arrival.
Flying was consistently cheaper on all 12 of the UK routes in the study, including domestic routes between London and Scotland.
The report blames these price differences on an “uneven regulatory playing field” that benefits low-cost airlines.
It said airlines can offer lower prices because they pay no tax on jet fuel, while train operators pay energy taxes and tolls in most European countries.
“Flying only looks like a bargain because the cost of pollution is so cheap,” said Dr Parr.