NEW DELHI- India's capital has decided to ban all unregistered internet taxi firms after a female passenger reported she was raped by a driver contracted to U.S. online cab company Uber, a government official said on Tuesday.

The case has caused uproar in India after it emerged that the suspect had previously been charged for rape but had obtained a character reference signed by a police officer that appeared to have been forged.

It has also revealed a total failure to regulate the booming market for online taxi services in India. The Delhi transport department has been slow to respond and, according to reports, sent its order banning Uber by fax.

In its ruling, published in a national newspaper, the department stated that only six registered radio taxi companies would now be allowed to operate in New Delhi.

"We have banned Uber. Another public notice will be issued tomorrow for banning all non-registered cab service providers. It's almost done," said Kuldeep Singh Gangar, spokesman of the Delhi transport department.

Uber was blacklisted in New Delhi on Monday after police said it had failed to run background checks on the driver, who was arrested three years ago in a similar case but later acquitted.

The arrested driver, Shiv Kumar Yadav, appeared in court on Monday and was remanded in custody for three days. Yadav had obtained a reference from the Delhi Police, but police spokesman Rajan Bhagat told Reuters the certificate "seems to be fake."

The fast-growing ride-hailing service Uber was valued at $40 billion last week after its latest funding round ahead of an expected initial public offering. In India, the company operates in 11 cities.

India's central bank had earlier rapped Uber for violating the country's credit card payment system by using a so-called one-step authorisation process while the regulator requires a two-step procedure. Uber later complied, calling the requirement "unnecessary and burdensome".

The U.S. company has also been dogged by controversy surrounding its aggressive approach to local governments and traditional taxi services.

On Monday, the U.S. West Coast city of Portland sued Uber to bar it from operating in the city. The company started operating in Portland on Friday without consent from authorities or any agreement over how it would be regulated.

India's Home Minister Rajnath Singh may issue a statement to parliament calling on India's federal states and union territories to ban Uber, the Indian Express newspaper reported.

UBER STILL ON

A representative for Uber said the company had not been officially notified of any ban in New Delhi and would issue a statement later on Tuesday. It was still possible to hail an Uber taxi in Delhi using the company's smartphone application.

Uber taxi driver Satish Kumar, who has been associated with the company for 11 months, told Reuters he works for another travel company that is enrolled with Uber. He was unaware of the ban.

"We will only consider a ban once our app stops working," said Kumar, whose company pays 20 percent of the fare to Uber.

"If it is banned, we will suffer losses. It is up to the authorities to do the checks. Why blame the company and make others suffer?" he asked.

Before joining Uber, Kumar said he was trained for two days on basic etiquette and using the mobile app. He only submitted a copy of his driving licence and identity card to the company. He was not interviewed.

Uber taxis were also violating norms by plying within the city despite having an all- India tourist permit that mandates only inter-state travel, a government official said.

"They have not made any efforts to get themselves registered. They have just tried to use the loopholes in the system to run a service and gain commercially," said a Delhi transport department official on condition of anonymity.

The state department had also received several complaints from other operators about how unregistered providers like Uber were violating norms and hurting their profits.