The U.K.’s advertising regulator is cracking down on what it considers greenwashing by fossil fuel giants. A handful of newspaper, TV and poster adverts from Shell, Repsol and Petronas International were banned in the country for touting investments in renewable energy without mentioning the extent of each company’s polluting activities.

Businesses in high-emitting sectors "need to be really careful” with environmental messages, said Guy Parker, chief executive officer of the U.K.’s Advertising Standards Authority (ASA), in an interview with Bloomberg Green. "Chances are you’re going to need to add some balance to your ads.”

All of the campaigns targeted by the ASA emphasize the oil companies’ ambitions on renewable energy. A TV commercial that ran in September for Malaysian oil major Petronas said it was "enriching lives for a sustainable future,” but the ASA said the ad failed to mention the company’s significant carbon emissions and gave the misleading impression that Petronas was already having a positive environmental impact.