A fierce debate was sparked in Oregon after Brittany Maynard announced she was to be helped to die early.
The 29-year-old spoke publicly about her need to die with dignity but Monsignor Ignacio Carrasco de Paula, head of the Pontifical Academy for Life, told the ANSA news agency that "dignity is something other than putting an end to one's own life".
He added: "Brittany Maynard's act is in itself reprehensible, but what happened in the consciousness we do not know."
The Monsignor did accept he should not judge Ms Maynard but he added "the gesture in and of itself should be condemned".