As reported by Sport1, the criminal charges were filed by Deutscher Tierschutzbund, the German Animal Welfare Federation, and has been granted by the public prosecutor's office.

Sebastian Thiele confirmed that investigations had begun against Schleu and Raisner.

The athlete Schleu is accused of cruelty to animals, and Raisner of aiding cruelty to animals.

Schleu had been leading in the women's modern pentathlon prior to the penultimate riding phase of the competition, before her horse Saint Boy refused to jump.

Raisner was sent home from the Games in disgrace after repeatedly striking the distressed horse, and last month found guilty by an International Modern Pentathlon Union (UIPM) Disciplinary Panel of violating Rule 4.6.8, under which a "pentathlete or team is disqualified for rapping or beating a horse and all other cases of cruelty and/or ill treatment of a horse."

She must attend a "coach education seminar" which contains a "humane treatment of animals" module before returning to any UIPM competition, and was warned a repeat could see her UIPM Coaches Certification Programme credentials removed.

Schleu faced criticism for her violent and repeated use of the whip and spurs, but was found not guilty of excessive use.

The UIPM has set up a Riding Working Group to review the equestrian element of the sport at Tokyo 2020, with recommendations to be presented to the governing body's Executive Board in November, before changes are put to the online Congress from November 26 to 28.

Klaus Schormann is the only candidate for the UIPM Presidential role at the Congress, and is set to be re-elected to the post he has held since 1993 for an eighth term.

He wrote about the horse-striking controversy in a guest blog for insidethegames last month.

"Within days, the UIPM had introduced new measures to improve horse welfare in our sport," Schormann said.

"A working group of the foremost experts has since been established and has set about exploring and addressing both the incidents during the women’s final and the proposed changes.

"As much as the incidents themselves were tough for our sport, the process of listening, learning and evolving and adapting to meet not just the moment but all those to come has been a positive experience.

"As I said at the time, UIPM remains fully committed to riding as an integral part of the modern pentathlon based on the vision of Baron Pierre de Coubertin and we look forward to doing so in an even safer, more secure way."

The People for the Ethical Treatment of Animals (PETA) called for all equestrian events to be removed from the Olympics after the incident involving Saint Boy and the death of Jet Set following a serious injury in the equestrian eventing competition.

At present, modern pentathlon riders are randomly assigned a horse and meet it only 20 minutes before going out to jump.

With such little bonding time between animal and rider, the jumping portion of modern pentathlon is often chaotic, with horses refusing to jump, clattering into barriers and unseating riders.

Britain's Kate French ultimately triumphed in the women's modern pentathlon at Tokyo 2020.