Toyota has announced a global recall of 1.9 million Prius hybrid cars over a fault with its speed control.
The world’s biggest carmaker said a software fault in a power converter might cause vehicles to slow down suddenly.
The Japanese firm said: “In limited cases, the hybrid system might shut down and the vehicle will stop, perhaps while being driven.”
However it tried to reassure owners by saying it is more likely the defect could activate the warning light system and “probably” cause it to enter “failsafe mode”.
It said cars could still be operated but with reduced power output.
“The car may stop while driving, but not suddenly,” a Tokyo-based company spokeswoman said.
“It would slow down, eventually to stop.”
Toyota confirmed it had identified at least 400 faulty vehicles, three-quarters of those were discovered in Japan.
In a UK blog post Toyota said the recall affects 30,790 third generation vehicles, manufactured between March 2009 and February 2014.
It said: “All the vehicles affected by this issue are being recalled so that the control software can be updated.
“Vehicle owners will be contacted by Toyota within the coming weeks by post or telephone and asked to make an appointment to bring their car to their nearest Toyota centre, in accordance with Vehicle and Operator Services Agency guidelines.”
It added that no road traffic accidents had been attributed to the fault.
A total of 700,000 Priuses are being recalled in the United States.
The US has also been issued with a recall of 260,000 2012 RAV4s, Tacomas and Lexus RX 350s over an unconnected potential braking issue.
Toyota and other Japanese car firms have suffered a series of high profile recalls in recent years, which has undermined their reputation for quality control.