David Carrick, 47, was previously charged with 44 offenses against 12 alleged victims, including rape, coercive and controlling behavior and sexual assault.
He is now charged with nine more crimes against a thirteenth alleged victim.
The new charges include false imprisonment, six counts of rape, indecent assault and possession of a firearm with intent to cause fear of violence. The charges relate to incidents that allegedly took place in 2003 and were reported to police in July 2022.
The firearms possession charge was filed before Carrick was employed as an armed police officer.
He will appear at Westminster Magistrates’ Court on November 30.
He remains in custody.
Carrick was originally arrested by Hertfordshire Police in October 2021.
He was immediately suspended and Herts Police launched an investigation.
Before his removal, he was attached to the Parliamentary and Diplomatic Guard Command.
A police statement said: “As part of the investigation, the matter was referred to the Independent Police Conduct Authority.
“The Met’s Directorate of Professional Standards continues to monitor developments closely and will provide any support to officers in Hertfordshire. National rules provide that any investigation into misconduct must await the outcome of a criminal case.’