Over 2,700 people have written to Eurostar to urge it to reverse a new policy which will force cyclists to dismantle their bikes before travelling, according to the UK's largest cycling charity.
CTC said it was "overwhelmed" by the support for its campaign, which was launched alongside its partners in France, Belgium, the Netherlands and Germany.
Currently cyclists can take a complete bicycle and pay a £30 fee for it to be carried on the cross-Channel rail service via a registered luggage system.
But from next month passengers will be forced to dismantle their bikes, put them into a box and reassemble them when they reach their destination. This is more restrictive than any train operator in the UK.
Eurostar claimed the change is needed to accommodate other passengers who are travelling with more luggage.
The European Cyclists' Federation (ECF), which represents cycling bodies across the continent, described the new policy as "extremely inconvenient".
CTC campaigner, Sam Jones, said: "We've been overwhelmed by the numbers of people who have supported CTC's call for Eurostar to reverse their planned policy.
"Over 2,700 people have written in support in just seven hours, showing Eurostar's ill-thought out policy has really touched a nerve across Europe's cycling community.
"In a meeting CTC and the ECF had with Eurostar a month ago, they admitted the changes would make travelling on Eurostar trains with a bicycle less convenient, but were adamant they would not budge. We hope that they will now realise their mistake."
CTC claim that the new policy will discourage new cyclists or those who rely on cycling as a mobility aid.
Eurostar has written to concerned passengers, telling them that "our staff are trained and ready to assist with the new procedure".
But Mr Jones warned: "We are concerned to what degree they have been trained. Only someone properly trained to reassemble a bicycle should be involved, anything else could leave them liable to a failure of duty of care."
Eurostar said the new policy will allow it to transport more bikes by train and all "reasonable size" bike boxes will be accepted.
A spokesman added: "Passengers with bikes have and continue to be important to us. Our new policy has been introduced so that we can use the space on our trains more flexibly, by carrying the same or more bikes depending on the demand from passengers.
"The only change is that bikes will now need to be carried in a bike box, which we are happy to provide. When packaging bikes in this way, they take up less space which means that we can carry more bikes or any other type of luggage."