A spokesman for Uber told the BBC the firm is not able to clarify how many United Kingdom drivers are included in the 2.7 million.
Uber says that the 2.7 million figure is an approximation because some users might disclose a different location to the one where they actually live. At the time, the company paid the hackers $100,000 and disguised the breach as a "bug bounty" to keep it quiet.
The lawsuit alleges that Uber experienced a smaller data breach in 2014 and, although the company vowed to update its security practices in order to meet industry standards, it failed to do so, leading to the 2016 breach, NBC Chicago noted.
Because Washington's data breach law does not define "personal information" as including names, email addresses, and telephone numbers, the complaint filed by Washington Attorney General Bob Ferguson relates only to the Uber drivers residing in Washington.
Ferguson said that the ride-sharing company violated state law by not informing consumers that their information had been stolen in the 2015 breach.More news: Microsoft unveils plans for a new modern headquarters
This comes following the admission of Uber that information of Filipinos were exposed in a massive breach involving 57 million users worldwide dating back to October 2016. If the breach impacts at least 500 residents, the business must also notify the attorney general's office within 45 days.
Ferguson's lawsuit is the first from a state, although attorneys general in New York, Missouri, Massachusetts, Connecticut and IL have begun investigations, and the city of Chicago and Cook County have filed a lawsuit. "There is no excuse for keeping this information from consumers". Almost 11,000 drivers in the state were affected.
The lawsuit was filed Tuesday in King County Superior Court. Under such a theory, he argues that Uber should face a penalty of several millions of dollars.
Digital minister Matt Hancock said in a written statement: "The government expects Uber to respond fully to the incident with the urgency it demands and to provide the appropriate support to its customers and drivers in the UK".