Companies on both sides of the Atlantic that indulge in "greenwashing" can expect to face increased scrutiny as watchdogs in both the US and UK signalled plans to crackdown on firms guilty of making false or exaggerated claims about their green credentials.

The US Federal Trade Commission (FTC) yesterday announced it was bringing forward plans for a review of its environmental marketing guidelines in response to "the current increase in green advertising claims".

The so-called green guides, which outline best practices for environmental marketing and cover how businesses should promote specific green claims such as degradability, recyclability and ozone safety, were scheduled to be reviewed in 2009 but the FTC said it would begin the review now to better ensure the guides "reflect today's marketplace".

The commission said that it was requesting comments about the guides' costs, benefits and effectiveness, as well as responses to more specific questions about how to define "sustainable" and "renewable" marketing claims.

The review will also incorporate a series of workshops, the first of which will be undertaken on 8 January and will address the marketing of carbon offsets and renewable energy certificates (RECs).

The marketing of both carbon offsets and RECs have faced stiff criticism over the past year, with many environmentalists claiming providers often struggle to adequately substantiate that the credits they sell are as environmentally beneficial as they claim. The FTC said it would seek to address this issue through the workshop, which will "explore advertising claims related to these products, as well as issues of consumer perception, substantiation and self-regulation".

The FTC announcement came just days after the chairman of the UK's Advertising Standards Authority (ASA) reiterated his commitment to cracking down on firms that make erroneous green claims in their advertising and marketing material.

Speaking to The Guardian in his first major interview since being appointed this summer, Lord Smith said he wanted the watchdog to be "more proactive and higher-profile" in its policing of green claims.

"Whether it's wind turbines or airlines or cars with claims about CO2 emissions, the claims have to be accurate and the companies have to be able to justify that," he said. "My message is that erroneous claims will not slip through the net."

Lord Smith admitted that assessing green claims was "almost virgin territory " for the organisation, but added that it was improving its ability to analyse environmental claims all the time and was committed to responding to growing public concern over "greenwashing".