The organization, which has historically praised the Tesla Model S and Model X, is cutting its ratings for both vehicles due to the automaker failing to update the software for certain versions of those models. The software update would have enabled automatic emergency braking for S and X models built since late October of last year.

Consumer Reports is tired of waiting for Tesla and is sending the maker of electrical vehicles a clear sign of its frustration.

An employee removes a wheel from a Tesla Model S automobile during driving unit fitting on the final assembly line at the Tesla Motors Inc. factory in Tilburg, Netherlands.

"When we purchased our latest test car, we were assured automatic emergency braking would be enabled by the end of 2016," said Jake Fisher, director of Consumer Reports' Auto Test Center.

"We've been waiting for this important safety feature, which is standard equipment on much cheaper cars."

Consumer Reports has given higher scores to vehicles with Automatic Emergency Braking (AEB) as a standard feature. The organization believes AEB reduces crashes and cuts the likelihood of serious injuries.

Now, after waiting several months for the safety feature to be enabled on the Tesla vehicles it owns, Consumer Reports is no longer ranking the Model S as the best of seven ultra luxury cars reviewed by the organization. The Model S score falls 2 points from 87 to 85.

Meanwhile, Consumer Reports cut the score of the Model Xfrom 58 to 56, dropping it to near the bottom of luxury midsize SUV's.

Consumer Reports says it received a statement from Tesla saying:

"Automatic Emergency Braking and other safety features are a top priority, and we plan to introduce them as soon as they're ready. We believe it would be morally wrong and counterproductive to our goal of improving consumer safety to release features before they're ready, and we believe our customers appreciate that."

A spokesperson for Tesla told CNBC the software update addressing emergency braking has begun.

Whenever the technology update takes place, Consumer Reports says it will review both Tesla vehicles again and may return them to the higher scores.