A spokesperson for the IOPC said: "We are carrying out an independent investigation following the arrest on Wednesday, 8 September, of a member of Sussex Police staff on suspicion of rape and misconduct in public office.
“The suspect was interviewed under caution and has been released on bail."
“No further details will be issued at this time.”
The IOPC did not confirm the identity of the person involved.
On Friday Sussex Police confirmed the arrest had been made on September 8, adding: "The matter has been referred to the Independent Office for Police Conduct (IOPC)and it is conducting an independent investigation."