Uber investors remain bullish after a landmark legal ruling in California that obliges the taxi app service to treat some drivers as full-time employees.

Backers of the start-up, which has been at the forefront of the so-called "sharing" economy, told the newswire Reuters that they believe Uber was no longer so dependent on the flexible workforce.

One investor argued that as the company matured it would be "just fine" for it to move its staff to more regulars hours, but declined to be identified because of sensitivity around the ruling.

Even if Uber had to pay costs associated with full-time staff, such as expenses and the Social Security federal insurance scheme, these would be offset by the low wages that the company’s drivers would receive, the source said.

In its judgement last week the Labor Commissioner’s Office in California found that Uber should have reimbursed a driver for expenses accrued during the course of her job, much like a full-time employer would.

The office awarded Barbara Ann Berwick roughly $4,000 (£2,500) for mileage and toll expenses during the course of two months work, in a decision that the taxi app firm is appealing to a state court in California.

In the past Uber has advertised itself as a market platform which connects prospective passengers and drivers, the latter being treated like independent contractors with responsibility for maintaining their own vehicles and paying their own expenses.

Its chief executive and founder Travis Kalanick has appeared undaunted by a wave of regulatory threats across North America, Europe and Asia, which include concerns such as drivers’ rights and passenger safety.

The company’s app is expected to generate some $10bn (£6.3bn) in sales for drivers by the end of this year, according to Business Insider, with the company keeping 20% of every payment, or $2bn (£1.3bn).