South Canterbury MP Jo Luxton has admitted causing a three-car crash on a state highway in her electorate.

Luxton, a Labour Party MP who represents Rangitata, confirmed to Stuff that the crash happened near Timaru last week after she failed to stop in time when another car slowed in front of her.

"While travelling through a 50kmh zone on State Highway 1, I failed to notice traffic and rear-ended a car which subsequently hit a car in front of it," Luxton told Stuff in a statement.

She said she was not using her cellphone at the time of the crash.

The crash happened at 12.30pm on October 11 while Luxton was travelling on State Highway 1 at Winchester, north of Timaru.

Luxton said she was not injured in the incident.

"After checking that the occupants were unharmed I returned to my car and retrieved by phone from my purse to call the police," she told Stuff.

Luxton confirmed she had given a formal statement to police.

She said at this stage no further action had been taken.

Police earlier confirmed the incident.

They told Stuff the vehicle responsible failed to see another car slow in front of it and "rear-ended it".

It was then shunted into another vehicle.

A police spokesperson said the crash was still under investigation.

Luxton is a second-term Labour MP. She entered Parliament as a list MP in 2017 and in 2020 she won the Rangitata electorate. The seat spans the areas of Timaru, Temuka and Ashburton.