Google has allegedly placed brand and government agency ads on several illegal and risk-prone websites, media reports say.

This has led to major advertisers considering to reduce spends on Google's third-party ad network. They are also demanding that the tech major brings in more transparent practices.

According to findings by Adalytics, over 36,000 sites could have been serving such ads. Of these sites, 8% were found to be risky for brands and several other were in danger of copyright violations.