Google operated a secret programme, known as "Project Bernanke," that relied on data from past bids in the search engine giant's digital advertising exchange and allegedly gave its own ad-buying system an edge over competitors, The Wall Street Journal reported.

The name of the secret programme got revealed in an improperly unredacted document Google had filed as part of an anti-trust lawsuit in Texas. The report on Saturday said that Google's programme was not disclosed to publishers who sold ads through the company's ad-buying systems.