Fiat is the latest brand to face criticism from the advertising regulator for environmental claims after it boasted of its cars' low carbon dioxide emissions in two press ads.

The Advertising Standards Authority also upheld complaints against Fiat for potentially misleading price claims because the models depicted in the ads were not available at the advertised price.

The press ads, which ran in February, featured two different headlines: "E CO2 NOMY OF SCALE" and "LESS CO2 NO CONGESTION CHARGE". In both ads the word "CO2" was coloured green.

Both ads depicted four models of Fiat, each described with a model name, price and specification.

The headlines prices, qualified with the word "from", were for bottom-of-the-range models, while the prices for the low CO2 emissions models featured in the ads were more expensive.

Although the actual prices were given in small print at the bottom of the ad, the ASA said it was a breach of the Committee of Advertising Practice code to quote prices that do not match the models pictured.

The ASA also ruled that the Fiat ads could give the impression that the models with low CO2 emissions were cheaper than they really were.

Fiat submitted research from Cleangreencars.co.uk as evidence that its cars had the lowest average CO2 emissions of any car manufacturer.

The ASA acknowledged this was true at the time of publication, while noting that the brand had since been overtaken by Mini in terms of lowest average CO2 emissions.

However, the regulator said the prices in the ads did not represent low CO2 emission cars and that they could mislead on those grounds.

Fiat's ads breached the CAP code on grounds of truthfulness, prices, comparisons, motoring and qualification of environmental claims, the ASA ruled.

The watchdog welcomed Fiat's assurance the ads would not be shown again in their current form and advised them to consult the CAP copy advice team in future.

Complaints to the ASA about environmental claims in ads have soared according to the organisation's annual report for 2007.

In 2007, the watchdog received 561 complaints about environmental claims in 410 ads, up from 117 complaints about 83 ads the year before.

Previously the ASA has censured companies such as Suzuki, Shell, Ryanair and Toyota for so-called "greenwash" where companies overstate their environmental credentials.

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