In a move that will send shivers down the spine of advertising execs the world over the Norwegian advertising watchdog has announced it is to ban the use of the words "green", "clean" and "environmentally-friendly" to describe cars on the grounds that "cars cannot do anything good for the environment except less damage than others".

The new rules will come into effect from October 15th with the threat of fines for those firms that continue to make excessive environmental claims for their cars.

The guidelines will also make it harder for manufacturers to compare the environmental performance of their cars, according to Reuters' reports.

Speaking to the news agency, Bente Oeverli of the Norwegian Consumer Ombudsman, said, "If someone says their car is more 'green' or 'environmentally friendly' than others then they would have to be able to document it in every aspect from production, to emissions, to energy use, to recycling".

Technically it is hard to argue with Norway's analysis - no car is truly green and even new electric cars have a carbon footprint. Moreover, the automotive industry has undoubtedly been guilty of considerable greenwash in the past and stringent advertising guidelines and tough policing are needed to stop manufacturers making excessive claims over the environmental credentials of their vehicles.

However, there is a danger that in developing such strict rules the authorities could inadvertently hamper development of more sustainable cars.

The primary driver behind the automotive industry's belated attempts to develop greener vehicles is not a concern over the welfare of the planet, but the fact that there is a growing demand for these vehicles.

Take away the opportunity to advertise this new generation of more fuel efficient vehicles as kinder to the environment and you potentially undermine that demand. Take away the demand and the biggest incentive for manufacturers to develop these types of vehicles also disappears. Why should manufacturers invest in developing a greener car than its rivals when it can't advertise that fact to its customers?

Norway's authorities may argue that proposed EU laws on improved fuel efficiency will force manufacturers to improve their environmental impact, but with their ability to advertise their green credentials curtailed where is the incentive for them to develop designs that go over and above the required EU standards?

That is not to say that you don't need rules to keep the greenwashers in check and it remains essential that all environmental claims made in adverts are independently verified. But effectively banning some of the most powerful words in the advertiser's lexicon seems a step to far. 

The one silver lining is that the decision by the Norwegian authorities could represent a timely warning shot to advertisers and marketing execs. The strict new rules have only been drawn up as a response to what the Consumer Ombudsman clearly regarded as excessive environmental claims from car manufacturers that it felt would mislead customers.

Firms advertising green products need to be fully aware that advertising watchdogs in all regions are keeping a very close eye on their claims. It may be tempting to overstate a product's environmental credentials but when doing so is only going to encourage yet more stringent regulations it is simply not worth the risk.