The consumer protection arm of the California Public Utility Commission found Uber Technologies has violated "zero-tolerance" rules governing drunken-driving complaints on 151 occasions over the course of a year, out of 154 complaints reviewed.

Uber's popular ride-sharing network has repeatedly failed to promptly suspend and investigate its California drivers when passengers report them driving drunk, state regulators charged in an enforcement action, recommending $1.13 million in fines.

In only 21 of those cases did the company conduct any follow-up driver investigation, the commission inquiry found.

The recommended fine for alleged violations is believed to mark the first such citation issued against the San Francisco-based ride-hailing network or its competitors since the rules were adopted in 2013.

The enforcement action follows a recent consumer backlash against the company and its senior management over a series of revelations about its corporate culture and business tactics,

including complaints of sexual harassment.

The drunken-driving findings, which stem from a review of passenger complaints lodged between August 2014 and August 2015, were contained in a nine-page investigative order issued by the commission's Consumer Protection and Enforcement Division on Tuesday.

Those charges and the proposed penalty are now subject to examination by an administrative law judge who will conduct further proceedings before recommending to the five-member commission itself what action, if any, should be taken against the company.

Uber spokeswoman Eva Behrend, noting that the report relates to complaints dating back two or three years, said, "We've significantly improved our processes since then."

"We have zero tolerance for any impaired driving," she said, citing Uber's "community guidelines," which state that any driver found to be under the influence of drugs or alcohol while on the job will be "permanently deactivated" from the network.

"Uber may also deactivate the account of any driver who receives several unconfirmed complaints of drug or alcohol use," it says.

According to the commission's own findings, the company received 2,047 zero-tolerance complaints statewide against its UberX and UberPool drivers during the year in question, and the

company dismissed drivers in 574 of those cases.

The company, which operates in 74 countries, says it currently has 147,000 drivers on the Uber platform in California, accounting for nearly one-fourth of its U.S. total.