The fine is expected to be the largest penalty ever levied on a single company by the US Federal Trade Commission (FTC), although Google makes a similar amount in revenue roughly every five hours, the Wall Street Journal reported.

Google and the FTC have reached a proposed settlement and agreed on a fine, but the deal awaits final approval by the regulators and could be changed before it is released to the public, the Journal said.

Google was accused in February of using special "cookies" to bypass Apple and Microsoft privacy settings, allowing the search giant to secretly track the surfing habits of millions of users and target them with ads.

Google stopped using the offending cookies after the allegations surfaced, and has characterised the situation as the unintended side effect of an effort to personalise Google accounts.