Toyota has said it is investigating possible braking problems in its luxury Lexus hybrid, the latest in a series of safety issues that have dented the Japanese car giant's reputation for making reliable cars.

Friday's move comes as US safety regulators begin a formal probe into possible brake problems with the company's flagship hybrid model, the Prius, which has the same braking system as the Lexus.

A Toyota spokesman said on Friday that the company had not received any complaints over the Lexus HS250h model, which went on sale in Japan in July and in North America in September, but was looking to "ensure safety for our customers".