Uber becomes one of the most valuable venture-backed startups in history

$50 billion valuation puts Uber on a par with Facebook before it went public

Uber has seen rapid growth thanks to its cheap rates and a user-friendly smartphone service (Getty Images)

Uber could be about to become one of the most valuable venture-backed startups in history after a fresh fundraising round may bump its worth up to around $50 billion.

That would make Uber one of the most valuable venture-backed startups in history, putting it on a par with Facebook, which was valued at $50 billion before its IPO.

The valuation hike comes just six months after the controversial taxi-hailing app notched up a $40 billion valuation after taking in another $1.2 billion from investors to fund its overseas expansion.

It is now looking at raising a further $1.5 billion, according to reports.

The start-up is reportedly hoping to use the cash to finance strategic moves, such as partnerships.

The cash injection would see it surpass Chinese smartphone maker Xiaomi - valued at $45 billion - as the world's most valuable privately-owned startup.

It would also top the market cap of public firms FedEx and Nissan, according to the New York Times.

The company, founded in 2008 by Stumbleupon creator Garrett Camp and Red Swoosh's Travis Kalanick has seen rapid growth thanks to its cheap rates and a user-friendly smartphone service.

It has raised around $4 billion along the way, allowing it to operate in more than 200 cities across the world and its cars to outnumber yellow taxis in New York.

It is facing a mounting pile of regulatory problems, however, including police investigations into its activities in China and France, as well as questions over its safety after one of its drivers was accused of rape in India.

Traditional taxi services, including London's black cabbies, have also protested against the app claiming its drivers do not have to comply with the same strict rules they do.

Uber's management have so far been undeterred by the setbacks and have ambitious plans for its future.

Kalanick, who also serves as its chief executive, has said the service could create 50,000 jobs in Europe in the coming year.