The firm’s largest-ever recall comes after a two-year investigation by federal safety regulator focused on autopilot function.

In a recall filing on Wednesday, the carmaker said autopilot software system controls “may not be sufficient to prevent driver misuse”.

“Automated technology holds great promise for improving safety but only when it is deployed responsibly,” said a spokesperson for the National Highway Traffic Safety Administration (NHTSA), which has been investigating the autopilot function for more than two years.

“Today’s action is an example of improving automated systems by prioritizing safety.”

The decision marks the largest-ever recall for Tesla, as autonomous vehicle development in the US hits a series of snags over safety concerns. The company has said that it will install new safeguards and fix current defects.

The recall covers models Y, S, 3 and X produced between October 5, 2012, and December 7, 2023.

Speaking before the US House of Representatives on Wednesday, acting NHTSA Administrator Ann Carlson said she was happy Tesla had agreed to a recall.

She said that the agency first started investigating Tesla’s autopilot function in August 2021 after hearing about several fatal crashes that occurred when the autopilot was on.

“One of the things we determined is that drivers are not always paying attention when that system is on,” she said.

Documents posted on Wednesday by the agency said the current autopilot design can lead to “foreseeable misuse of the system,” and that the changes to be instituted will “further encourage the driver to adhere to their continuous driving responsibility”.

Some experts have raised questions over whether such steps go far enough.

“The compromise is disappointing,” Phil Koopman, a professor of electrical and computer engineering at Carnegie Mellon University who studies autonomous vehicle safety, told The Associated Press.

“Because it does not fix the problem that the older cars do not have adequate hardware for driver monitoring.”

Driverless cars, exalted by supporters as an exciting technological advancement, have faced a series of setbacks in recent months.

In October, California suspended testing by the self-driving car firm Cruise, after California’s Department of Motor Vehicles (DMV) raised questions about safety concerns.