British dressage star Charlotte Dujardin withdrew from the Paris Olympics on Tuesday after a video emerged allegedly showing her mistreating a horse.

Dujardin, a three-time Olympic champion and the joint most-decorated British woman Olympian, said she had made an "error of judgement" and expressed deep remorse.

The International Federation for Equestrian Sports (FEI) suspended her with immediate effect, just days before the start of the Games.

The governing body said it had received a video "depicting Ms Dujardin engaging in conduct contrary to the principles of horse welfare".

"This video was submitted to the FEI by a lawyer representing an undisclosed complainant," the FEI added.

"According to the information received, the footage was allegedly taken several years ago during a training session conducted by Ms Dujardin at a private stable."

The FEI said Dujardin had confirmed she was depicted in the video and had acknowledged that her conduct was "inappropriate".

It said she had asked to be provisionally suspended pending the outcome of the investigations and voluntarily withdrew from the Paris Olympics. (AFP)