David Carrick, 47, had previously been charged with 44 offences against 12 alleged victims including rape, coercive and controlling behaviour and sexual assault.
He has now been charged with a further nine offences in relation to a thirteenth alleged victim.
The new charges are 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 alleged to have occurred in 2003 that were reported to police in July 2022.
The allegation in relation to possession of a firearm predates Carrick’s service in an armed policing role.
He will appear at Westminster Magistrates’ Court on 30 November.
He continues to be remanded in custody.
Carrick was initially arrested by Hertfordshire Constabulary in October 2021.
He was immediately suspended and Herts Police launched an investigation.
Prior to his suspension, he was attached to the Parliamentary and Diplomatic Protection Command.
A police statement said: “Referrals have been made to the Independent Office for Police Conduct as the investigation has progressed.
“The Met’s Directorate of Professional Standards continues to monitor developments closely and will provide whatever support it can to Hertfordshire officers. National regulations dictate that any misconduct proceedings must await the outcome of the criminal case.”