An national press ad created by Publicis promoted Renault's electric cars and claimed that the Renault Fluency ZE model would help reduce emissions by at least 90%, compared to a current diesel model.
In small print, Renault supported the claim by comparing the electric car with a Renault Megane Hatch.
The Advertising Standards Authority received one complaint that the ad was misleading because the 90% figure was based on the French electricity generation mix, which had significantly lower levels of CO2 emissions than electricity produced in the UK.
In response, Renault argued that the ZE model would be available in the UK in 2011 and that the ad merely attempted to draw comparisons between internal combustion engines and their effects, versus electric vehicles.
Renault added that given electric vehicle sales in France were likely to outweigh UK sales significantly, it was not misleading to make reference to the source of electricity being the French average mix.
The ASA said it noted that Renault had qualified its claim, explaining that the savings figure was based on circumstances in France.
However, it concluded that that readers were unlikely to understand the difference between electricity generating mixes in France and the UK, and how that would affect CO2 savings in different countries.
The watchdog decided to ban the ad after it concluded, as the figure was not representative of CO2 savings typically in the UK, that the ad was misleading.
Last month, Renault had a TV ad for its electric cars banned for claiming they were zero emissions vehicles. The ASA adjudicated that if the car was charged using energy sourced from the UK's national grid, CO2 emissions would be produced as a result.
This article was first published on campaignlive.co.uk