At a time when Toyota Motor Corp. is trying to regain consumer confidence following a series of large recalls and federal probes into safety defects, Consumer Reports on Tuesday warned shoppers not to purchase one of the company's upscale Lexus models because of a rollover risk.

The magazine, which for years has recommended most Toyota vehicles, said the Lexus GX 460 SUV failed a key emergency-handling test and issued a rare "Don't Buy" warning.

The last time the Yonkers, N.Y., magazine, famous for its independent testing of autos and buyer recommendations, issued such a warning was in 2001, when it said that the performance of a Mitsubishi Montero Limited was "not acceptable."

The caution not to purchase the Lexus GX SUV comes as Toyota is using aggressive financing and lease incentives to spur sales of its Toyota-branded vehicles and regain market share lost to safety concerns. The Japanese carmaker has issued nearly 10 million recall notices worldwide in recent months for problems related to sudden acceleration that it blames on sticky gas pedals and faulty floor-mat design as well as braking problems in some hybrid models.

Last week the U.S. Department of Transportation said it would seek the maximum civil fine of $16.4 million against Toyota for delays in notifying authorities about defects in its gas pedals.

Consumer Reports said that it testing staff found that "when pushed to its limits on a handling course" on the magazine's test track, the rear of the Lexus GX "slid out until the vehicle was almost sideways" before the vehicles electronic stability control system was able to regain control. All four of the magazine's test drivers experienced the problem.

The magazine said such a situation could happen in "real-world driving" and that it could lead to a rollover accident.

The phenomenon, known as "lift-off oversteer" could occur "when a driver enters a highway's exit ramp or drives through a sweeping turn and encounters an unexpected obstacle or suddenly finds that the turn is too tight for the vehicle's speed," Consumer Reports said.

"A natural impulse is to quickly lift off the accelerator pedal. If that were to happen in the GX, the rear could slide around far enough that a wheel could strike a curb or slide off the pavement," the magazine said.

Consumer Reports contacted Toyota and was told in an e-mail response that the automaker was "mystified by the results of Consumer Reports testing on the Lexus GX 460."

After the magazine issued its do not buy warning, Toyota posted a statement on its website saying that it was "concerned with the results of Consumer Reports testing on the Lexus GX 460 and their suggested buyer recommendation."

Toyota said its engineers conducts similar tests and believes "these procedures provide a good indication of how our vehicles will perform in the real-world; however, we will try to duplicate the Consumer Reports' test to determine if appropriate steps need to be taken."

The automaker said that the vehicle "meets or exceeds all federal government testing requirements."

The report will "scratch the scab" starting to cover Toyota's efforts to shore up its brand name and image, said James Bell, an analyst for auto information company Kelley Blue Book.

It "comes at time when many within Toyota must have been breathing at least a little easier," he said.

Recent tracking of consumer attitudes by Kelley had found that safety concerns about the Toyota and Lexus brands were starting to wane before this latest warning, Bell said.

Consumer Reports, which tested a Lexus that it had purchased to review, said no other SUV it has tested in recent years has slid out as far as the GX 460, "including the Toyota 4Runner, which shares the same platform as the GX." It found the same problems in a second vehicle it obtained to double check its findings.

The magazine said it has reported its concerns to the National Highway Traffic Safety Administration.

The GX 460 has been on sale for about three months and about 5,000 vehicles have been sold, according to Consumer Reports. The magazine said it is not aware of any injuries or accidents resulting from the alleged flaw.

Generally, Toyota vehicles have performed well in Consumer Reports tests. A year ago, Consumer Reports recommended 22 of the 25 Toyota products it tested, more than any other manufacturer. But because of the recalls, the magazine only recommended 13 of 26 Toyota models this year.