Detective Constable Justin Gilmore, aged 52 and attached to Met Operations, was convicted at Inner London Crown Court on Wednesday, 8 November following an investigation by officers at Central South Command Unit.
He remains suspended from duty.
Commander Ben Russell said: “This is an allegation from eight years ago but no less serious with the passage of time, and we are extremely grateful to the victim for coming forward to enable us to bring DC Gilmore before the courts. She has been incredibly brave and we would urge anyone in a similar situation to come forward so we can help, support and investigate.
“This type of behaviour is completely unacceptable and we are committed to ridding the Met of those who should not be here.
“DC Gilmore will now face a gross misconduct hearing as soon as possible.”
DC Gilmore was charged on 14 December 2022 with sexual assault on a female colleague while the pair were off-duty at a social event in Southwark on 22 July 2015. DC Gilmore was based at Southwark police station at the time.
The matter was reported to police on 6 January 2022 and DC Gilmore interviewed under caution before later being charged and suspended from duty.
He was found guilty by a majority verdict and sentenced by the court to a £1,000 fine and £1,500 costs.