Automakers topped the list of the greenest global businesses when Interbrand released its annual list earlier this week.

But while the industry has made gains, it isn’t a bastion of green policies and often fights the efforts by regulators to reduce emissions, according to some environmentalists.

“The question remains as to whether the auto industry continues to invest in fuel economy and zero emission technologies or will they fight back whenever there is a periodic review,” said Simon Mui, director of the California vehicles and fuels office at the Natural Resources Defense Council.

Toyota, followed by Ford and Honda claimed the top three spots on the brand consulting firm’s list, which measures companies against two criteria: their ability to demonstrate that they source and produce products in an environmentally responsible manner and the consumer perceptions of their environmental credibility.

There are probably two reasons why automakers score so well.

First, they sell products that gobble up oil and spew pollution and they are constantly telling consumers worldwide how they are making improvements to reduce consumption and emissions.

Fuel economy is among the top shopping considerations among car buyers, so as they compare how well various vehicles and brands do on that score, consumers develop a perception of an automaker’s green credentials.

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This is reinforced by how much money the car companies pour into advertising green products such as the Nissan Leaf electric car, the Toyota Prius hybrid and the new C-Max and Fusion hybrids from Ford.

Second, it’s easier to measure the efforts by automakers to clean up their business, said John Viera, global director, sustainability and vehicle environmental matters, and that plays well into the way the Deloitte accounting firm audits the sustainability records of companies.

Most of these “green rankings should be taken with a grain of salt,” Mui said.

Honda pops up third on the list but has worked behind the scenes to undermine California’s zero emission vehicle requirements that mandate that automakers sell more electric and other vehicles that don’t emit pollution.

The auto industry also has been problematic at times, especially when getting in fights with regulators over California’s authority to set green car standards, Mui said.  

Ford, however, has stood out in developing environmental credentials, he said.

“Ford has actually been a good player in the automotive industry,” Mui said. “Their management and corporate officers see the need to address climate change and they know the automotive sector is a vital component of doing that.”

Ford issued its annual sustainability report Friday, listing its environmental achievements and goals. It has been producing the report since 1999.

The automaker has slashed CO2 emissions at its global facilities by 37% per vehicle between 2000 and 2012 and plans for a 30% reduction from 2010 to 2025. It will do that by reviewing all of its operations including the new model cars it sells and the technology and processes it uses to make those vehicles.

Ford said it buys into the goal of keeping CO2 levels in the Earth’s atmosphere at or below 450 parts per million – a level the scientific community believes will help avert the most serious effects of climate change.

The automaker’s sustainability drive includes other metrics besides CO2 levels. It says it has trained about 2,100 suppliers to meet certain human rights and working condition requirements. It has cut global use of water per vehicle produced to 4.3 cubic meters (one cubic meter equals 264 gallons) in 2012 – down from 4.7 cubic meters in 2011.

This all makes good business sense, executives say.

Customers and stakeholders are holding businesses more and more accountable for sustainability performance, and businesses are working hard to ensure that their external perception reflects their internal efforts,” said David Pearson, Deloitte’s global sustainability chief.

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