It used to be easy to spot what environmentalists call 'greenwash' - unsupportable claims for the ecological friendliness of a product or service. But, as the accusations and counter-accusations fly, it's becoming increasingly difficult to separate green wheat from marketing chaff. Greenwash was rife in the 1980s and 1990s. During this period, growing concerns about climate change and environmental damage boosted the influence of Greenpeace, Friends of the Earth, WWF (formerly the World Wildlife Fund) and other non-governmental organisations (NGOs) determined to subject business's environmental claims to harsh scrutiny. When the mainstream press and TV latched on to the practice, business almost completely stopped making the unverifiable claims. This has changed in recent years, however, as the environment has shot to the top of the political agenda. In 2006, the UK's Advertising Standards Authority (ASA) received 117 complaints about environmental claims in 83 adverts. In 2007 it received 561 such complaints about 410 ads. Oil companies and airlines topped the list of ASA transgressors, but car manufacturers are well represented too.