Helium balloons are causing hundreds of train delays at a cost of £1m in taxpayer money every year, Network Railhas said.
The party favourites are becoming tangled in high voltage wires above rail lines after being released into the air, the company claims.
It says there were some 619 so-called ‘balloon incidents’ on the network last year alone. Many of those resulted in significant hold-ups because removal from cables often requires the line's electricity to be switched off.
And the company – which runs Britain’s railway infrastructure – further warned that passengers who bring such balloons to railway stations may unwittingly be risking tragedy.
"If you're on a platform with a foil balloon filled with helium on a string and it comes in contact with the overhead wires carrying 25,000 volts, that could cause huge injury or death," said James Dean, chief operating officer for Network Rail's London North Western route.
"Ideally, we'd ask people not to bring balloons into our stations at all. Alternatively, carry them in bags so the risk of them floating upwards is minimised."
Network Rail made the warning as part of an awareness campaign around the issue.
The latest incident, it reported, took place this week at Smethwick Rolfe Street Station, in the West Midlands, when a float-away helium balloon got wrapped around overhead wires.
It caused hundreds of passengers on a number of trains to be delayed, and cost £5,000.
Balloon artists have also joined the campaign.
George Oustayiannis, of the National Association of Balloon Artists and Suppliers, said he believed a ban on releasing balloons should be implemented across the country.
He said: “Balloons bring fun and colour and a sense of celebration to any event, but please dispose of them responsibly, and never release balloons into the atmosphere. Respect the environment and prevent unnecessary danger and delays – please don't let go."
