The global method of instantaneous communication was "intended for adults", Auxiliary Bishop of Westminster John Sherrington told reporters on Friday.
Bishop John spoke as English and Welsh Catholic leaders officially endorsed a call by Pope Francis for governments and internet companies to better-protect children from "multiple dangers" posed by the internet.
Following a three-day meeting in Leeds this week, the bishops announced their support for the Declaration of Rome which was issued by the Vatican in October.
They said in a statement: "We challenge internet providers to take account of their responsibilities and to invest in measures to limit and control the deeply damaging ways in which the internet is used."
Leaders warned that "damaging consequences" have arisen from "unthinkingly" making the internet available to children.
Their statement continued: "We now see so many people acknowledging that they are addicted to its use and to the pornography which is so readily available there.
"The internet has also become a major means of the abuse of children, of blackmail and new forms of degrading slavery."