NEW YORK (CNN/Money) - People in most small SUVs are likely to be seriously injured or killed in side-impact crashes, according to a report by an insurance group Tuesday.

The Subaru Forester performed the best in a side impact crash test performed by an insurance group.

The Insurance Institute for Highway Safety, a nonprofit research group funded by auto insurers, gave "poor" ratings to seven sport/utility vehicles that it ran through crash tests. Many of those vehicles had received good ratings in separate side-impact crash tests run by the federal government.

The vehicles receiving the lowest rating of "poor" were: the Toyota RAV4; the Suzuki Vitara, as well as two twin vehicles, the Grand Vitara and the Chevrolet Tracker; the Land Rover Freelander; the Mitsubishi Outlander; the Saturn VUE; the Honda Element; and the Ford Escape, when not equipped with an optional side-impact airbag.

When equipped with that airbag, the Escape got the top rating, "good", as did the Subaru Forester, which also has a side-impact air bag. Ford said about 20 percent of buyers of the Ford Escape buy the optional side impact air bag. However, the side airbag is standard in the Subaru.

The Hyundai Santa Fe got an "acceptable" rating, while two other models, the Honda CR-V and Jeep Wrangler, got "marginal" ratings.

The institute uses a moveable barrier that is crashed into the side of the vehicles to simulate an impact from a large SUV or pickup truck.

But the institute's barrier is set somewhat higher off the ground than the barrier used in similar government tests, and it produced far worse ratings than the results from the National Highway Transportation Safety Administration (NHTSA), part of the Transportation Department.

For example, the NHTSA side-impact tests gave its best five-star rating for both the front- and rear-seat occupants for the Toyota RAV-4, the Saturn VUE, the Ford Escape and the Honda CR-V.

The Chevy Tracker and its Suzuki twins got four-star ratings for the risk to front-seat occupants and five-star rating for the rear-seat occupants. The Land Rover Freelander, the Mitsubishi Outlander, the Jeep Wrangler and the Honda Element have yet to be tested by the federal agency for side impact damage.

"It [difference in ratings] is not surprising because the tests are different," Institute Vice President Joseph Nolan said. "We're assessing the likelihood of head injury when struck by a high-ride vehicle, and we're using more sensitive crash dummies. We feel they do need to upgrade their standards."

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But Mark Bilek, automotive managing editor for Consumer Guide, said that the IIHS test is a worst-case scenario, and that the poor ratings in this instance shouldn't necessarily scare buyers away from these models.

"The test is not as realistic as it could be," said Bilek, whose publication does not accept advertising from automakers or dealers. He said the movable barrier that the IIHS uses has less give to it than another vehicle, which is designed to crumple on impact. And he said the higher impact zone is not necessarily the best indicator of an accident with a larger vehicle.

"In most side impact, the impacting vehicle is full on brakes, which forces it lower," he said. "There's nothing wrong with giving people this information. Just don't make it your only decision on buying the car based on it. You should look at NHTSA and other information as well."

This is the first time that the Institute has done its own side impact test on new vehicles. It intends eventually to perform the tests on all types of vehicles, including larger SUVs, other light trucks and passenger cars. But it has conducted front impact crash tests on most vehicles.

Nolan said the "poor" rating signifies significant risk of injury or death for the occupants, while even the "marginal" rating also suggests a large risk of injury, although somewhat less risk than those with a "poor" rating.

Ford issued a statement pointing out the good rating received by the Escape with a side air bag, as well as the good rating it had received in the federal crash test and other independent tests.

"Ford has designed the vehicle to provide a high level of occupant protection in a wide range of real-world crashes, including side impacts," Ford's statement said.

Some automakers also questioned the design of the IIHS's test.

"GM believes this single test is not indicative of the vehicle's overall safety," said a statement from the world's largest automaker. "The rating is a single data point resulting from a very severe crash event. Most consumers will not be in a crash of this severity. In the real world, this type of collision occurs in only about 5 percent of all side crashes."

Other automakers also expressed doubts about the validity of the tests.

"The new 31 mph side impact test being conducted by the Insurance Institute is an extremely severe test that has not been recognized or adopted by any automotive manufacturer or government entity," a statement from Mitsubishi Motors North America said.

Chrysler also defended its Jeep Wrangler's safety and said it would work with IIHS "to better understand how this new test and rating scheme will relate to real-life accident scenarios."

Even Hyundai, which received an "acceptable" rating in the test, questioned the procedure. "While we may not be in complete agreement with the testing methodology used by IIHS, we understand and share their desire to provide safe vehicles for motorists in the U.S.," the Korean automaker's statement said.

Not surprisingly, the one automaker endorsing the test was Subaru, which had the best-rated vehicle.

"We believe the IIHS test provides a valuable third-party measure tool for the both consumer and the industry," Subaru spokeswoman Lisa Fleming said.

In front-impact crash tests the institute has conducted in the past among the small SUVs, only the Subaru Forester received a "good" rating for both side and front impact.