Bishop Hugh Gilbert has written to Nicola Sturgeon asking her to uphold freedom of conscience after SNP MP Dr Lisa Cameron was subjected to abuse over her vote against the legalisation of abortion in Northern Ireland.
He urged Scotland's First Minister to offer a "public reassurance" that pro-life views would be protected in the public square.
"I believe I write on behalf of all who cherish freedom of conscience within the public square and hold in high regard those in public life who remain true to their conscience, even at the expense of personal popularity or political advantage," said the bishop, who is president of the Catholic Bishops' Conference of Scotland.
Dr Cameron was one of the few MPs in the House of Commons last week to vote against extending abortion to Northern Ireland if its devolved assembly remains suspended by October 21.
The MP for East Kilbride, Strathaven and Lesmahagow said her office had received over 900 abusive messages following her vote.
She said on Twitter that the abuse had been "vitriolic" and that she feared being de-selected by "abusive party activists".
"Many thanks for all of your support. It means a great deal. This was a free vote of conscience however, the abuse I have suffered over the last 24 hours has been vitriolic. I have already been threatened by an individual that they are coming over to 'abort me'," she said.
An SNP spokesman told The National newspaper that no candidates would be rejected for selection on the basis of "religious views".
"As has been longstanding practice in the SNP votes on this issue are conscience votes for elected members, meaning it is entirely up to the individual member how they vote," the spokesman said.
"No-one is failed at assessment because of their religious views. Ordinary party members may disagree with the actions of a parliamentarian, but they should do so respectfully."