Benzi Gopstein, who heads the far-right Lehava organisation and has been arrested a number of times, made the comments in an article on the ultra-Orthodox Jewish website Kooker.
“Christmas has no place in the Holy Land,” wrote Gopstein, who lives in a Jewish settlement in Hebron in the occupied West Bank.
He spoke of the “fall of the line of defence of the Jewish people for hundreds of years against our enemies, the Catholic Church.”
“The mission of those vampires and bloodsuckers remains. If Jews cannot be killed, they can be converted,” he wrote.
“We must remove the vampires before they drink our blood once again.”
The Coalition Against Racism in Israel and others have called on authorities to investigate Gopstein.
In August, Israeli police questioned Gopstein after he condoned torching churches amid an uproar over recent hate crimes, including the firebombing of a Palestinian home that killed a toddler and both his parents.
On June 18, an arson attack occurred at a shrine on the shores of the Sea of Galilee in northern Israel where Jesus is believed to have performed the miracle of loaves and fishes.
Israeli prosecutors have charged three Jewish extremists in that case.