The Roman Catholic Church in England and Wales is urging voters to judge candidates for the local and European elections on their moral stances.
The cardinal is worried about a "culture of death"
The call comes in the church's new pamphlet, Cherishing Life, which warns of a slide towards a culture of death.
Cardinal Cormac Murphy O'Connor, the church's leader in England and Wales, said voters should draw on religious teaching when they come to vote.
The new pamphlet particularly opposes abortion and euthanasia.
It recommends voters ask candidates about their views especially on issues "where innocent lives are at risk".
'Culture of life'
Cardinal Murphy O'Connor pointed to the 180,000 abortions a year, calls for euthanasia and stem cell research, as he said it would be foolish not to raise the alarm.
He told BBC Radio 4's Today programme: "We all have a responsibility to create a culture of life.
"We are creating the culture that diminishes life and that is a terrible thing.
"If we don't commend life, we don't protect life, we don't enhance life, if we don't try to live the good life, then in fact we diminish it."
Later the cardinal said the church was not a "one issue" institution opposing abortion.
"However, we have said in this document that abortion is a priority
- and a very, very, very important one - and therefore that would have to be
taken into account, among others, by those who are going to vote in the election
with regard to the views of the candidate," he continued.
Cardinal Murphy O'Connor said the pamphlet was designed at countering the misapprehension that the Catholic faith was all about guilt and showing it was concerned with life and love.
Liberal Democrat MP Evan Harris, a member of the National Secular Society, said it was right for the church to get involved in political issues.
But he told Today: "I don't think religion has a monopoly on morality.
"In fact, as far as homosexuality goes, I think the Catholic church's position is immoral, I think it discriminatory and it's unfair...
"Their approach on the use of condoms in Africa I think is causing death actually, rather than proclaiming life because they have a doctrinal position."
Religious groups' concerns should not be given primacy in political debates, argued Dr Harris.