Thousands of bikes sit in an empty lot in Nunawadding. oBike launched in Melbourne in June, 2017. Credit:Jason South

Frustrated oBike customers fear they'll never see their $70 deposits again after it emerged the company has allegedly been converting deposits into subscriptions.

The Singaporean bike service withdrew from the Melbourne market several weeks ago after strict rules were imposed on the company by the state's environmental authority.

On Monday, the company issued a statement saying it would also stop operating in Singapore after the country's Land Transport Authority slapped it with new, strict guidelines.

"It is with deep sadness that we have to pull out of the Singapore market," the company wrote in a statement on Facebook.