The screen legend christened the MSC Divina in France in May (12) and members of the No Big Ships Venice Committee have asked her to support a campaign to stop the 139,500-tonne ship from cruising close to the picturesque Italian city.
They claim the wake from the vessel in the Venice lagoon, which surrounds the city, will harm historic canal-side buildings.
The letter reads, ""We can't believe that you want your name, which is a legend in Italy and the world, to be associated with a ship that contributes to the destruction of Venice, part of humanity's heritage. We are asking you to give up your role as godmother of the ship. Venice and the world would see that as a divine gesture.
""Venice belongs to the world. Help us save it... Venice and its lagoon are both world heritage sites and risk an environmental disaster every day because of the passage of these monsters of the sea.""
The MSC Divina also boasts a first-class suite named after Loren and decorated with pictures of the Oscar-winner throughout her career.