Monserratte, who represents St Cruz constituency, was expelled from party on March 11, 2015 for hobnobbing with the BJP during a bypoll held for Panaji seat.
He was arrested on May 5 on the charge of raping the 16-year-old and also booked for trafficking.
"Congress party took right decision at right time to expel him or else the current charges against him would have come as a major embarrassment to the party," Congress' Goa spokesman Urfan Mulla told reporters.
Monserratte is currently in the custody of crime branch. He would be presented before a local court tomorrow.