Google has been sued in the US over claims it illegally invades the privacy of users by tracking people even when they are browsing in "private mode". The class action wants at least $5bn (£4bn) from Google and owner Alphabet. Many internet users assume their search history isn't being tracked when they view in private mode, but Google says this isn't the case. The search engine denies this is illegal and says it is upfront about the data it collects in this mode. The proposed class action likely includes "millions" of Google users who since 1 June 2016 browsed the internet in private mode according to law firm Boies Schiller Flexner who filed the claim on Tuesday in federal court in San Jose, California.