Toyota may sell more hybrid vehicles than any other car maker but an environmental group in the US is targeting the company anyway, saying the average fuel economy of Toyota vehicles is worse than it was 20 years ago.

According to the Associated Press (AP), San Francisco-based Bluewater Network, which advocates government action to reduce dependence on fossil fuels, plans to run newspaper ads this week with the headline, "Is Toyota a Wolf in Sheep's Clothing?" The ads reportedly feature a photograph of Toyota president Katsuaki Watanabe alongside a wolf in a business suit.

According to AP, Bluewater Network says Toyota belongs to organisations that are suing California over its new smog regulations. It also says Toyota's vehicles are becoming less fuel-efficient. According to a recent report by the US Environmental Protection Agency, the average fuel economy for Toyota's fleet was 30 miles per (US) gallon in 1985 and is 27.5 miles per gallon this year.

"Is this the same company that brought us the hybrid Prius, claiming to be an environmental leader?" the ad reportedly asks.

The Associated Press noted that Bluewater Network took on Ford in 2003 after the automaker reneged on a promise to increase the fuel economy of its vehicles by 25%, but this is the first time Toyota has been a target of similar ads.

Toyota spokeswoman Nancy Hubbell told the news agency the car maker was surprised and disappointed.

"We certainly think of ourselves as an environmental leader," Hubbell reportedly said.

Hubbell acknowledged to AP that Toyota's average fuel economy has fallen in the last 20 years, but said that's because the mix of vehicles has changed and now includes trucks and sport utility vehicles.

"Toyota's line of vehicles has definitely changed, but that's based on consumer preferences," Hubbell told AP.

Hubbell said Toyota does belong to two alliances that are suing California over its new standards. But she told the news agency that's because Toyota wants the federal government - not states - to pass tough new national standards.

Danielle Fugere of the Bluewater Network told the Associated Press Toyota should simply adopt California's tougher standards instead of fighting them, especially since 10 other states are considering adopting those standards.

Fugere reportedly also criticised Toyota's hybrid SUVs, the Highlander Hybrid and the Lexus RX400h, saying their fuel economy isn't much better than their non-hybrid counterparts. Toyota says the economy is still better than many passenger cars.

"We think that misleads the public who believe hybrid technology comes with a fuel efficiency increase," Fugere tols AP, adding: "Toyota is not fulfilling its promise."

John Barker, president of New York-based DZP Marketing, questioned Bluewater Network's strategy and told AP the ads will likely have little impact.

"By inexplicably taking on one of the acknowledged leaders of the environmental movement, they discredit themselves and their cause," Barker told the Associated Press.