France's data privacy watchdog has handed out its biggest ever fine of €100m to Alphabet's Google for breaching the country's rules on online advertising trackers (cookies). 

The CNIL said in a statement today it had also fined US e-commerce giant Amazon €35m for breaching the same rules. 

The regulator found the French websites of Google and Amazon did not seek the prior consent of visitors before advertising cookies were saved on computers, it said in a statement. 

Google and Amazon also failed to provide clear information to internet users about how the two firms intended to make use of such online trackers and how visitors of their French websites could refuse any use of the cookies, the watchdog said. 

The CNIL said Amazon and Google had three months to change the information banners. If they failed to do so, they would face an additional fine of €100,000 a until the modifications are made. 

The financial penalty against Google is the biggest ever issued by the CNIL, a spokesman for the watchdog said. 

The previous record fine of €50m also targeted the US tech giant for breaching European Union data privacy rules.