An investigation has been launched after yellow Ofo bikes appeared on sale on Facebook for £50.
The scheme was launched in Sheffield in January with a fleet of 1,000 bikes; the company's first in the north of England.
Users download a free app to locate and unlock a nearby bike, which then charges 50p per half hour to use.
Despite the bikes only being available for hire, Daniel Capewell discovered one being advertised on Facebook for sale for £50.
Ofo have launched an investigation into the incident and have stressed that the bikes are only available to hire and are not for sale.
Matthew Sparkes of Ofo said: "Our bikes are for hire, not sale, so this attempted sale was reported to the police and is currently being investigated.
"Fortunately, we've found that the vast majority of people in Sheffield have enjoyed using ofo responsibly and our fleet of 1,600 bikes is in high demand."
Many Ofo bikes have been subjected to vandalism since the scheme's introduction with some found dumped in rivers, up in trees or with their locks broken off.
Last week, a Sheffield resident said he saw a pick-up truck overflowing with Ofo bikes being driven out of the city and fears they've now been melted down for scrap.
Yesterday, the Star revealed how five bikes had been found trashed and dumped on Wade Street in Page Hall.
Ofo spokesman Adam Rose said: “We've been operating successfully in Sheffield for many months and local reaction to the scheme has been hugely positive.
"There has inevitably been a small amount of misuse of our bikes, but levels of vandalism are low.
"The vast majority of our fleet in Sheffield is being used in a responsible and considerate manner, and we would never allow the actions of minority to ruin the scheme for Sheffield.”