The leader of Scotland’s Roman Catholics has told politicians that they should not expect to remain full Church members if they defend the “social evil” of abortion.

Using language calculated to shock, Cardinal Keith O’Brien likened the abortion rate to “two Dunblane massacres a day” and urged his followers to reject MPs and MSPs who supported the abortion laws.

The Cardinal went farther than any Catholic leader yet on the politics of termination during a sermon in Edinburgh marking the 40th anniversary of the 1967 Abortion Act in which he urged parliamentarians to stop supporting an “unspeakable crime”.

After the Mass at St Mary’s Cathedral, the Cardinal said that he would like to see the law changed. “I think it’s far beyond time that the present Abortion Act of 40 years ago was reexamined,” he said.

“We are killing – in our country – the equivalent of a classroom of kids every single day. Can you imagine that? Two Dunblane massacres a day going on and on. And when’s it going to stop?”

He denied that he was saying that Catholic politicians who backed abortion should be cast out from the Church. “I’m not going to say that to those who are involved in any way in aiding abortion, whether it’s mothers or fathers, politicians, doctors or nurses. They must consider their own consciences and whether or not they can approach the altar to receive Holy Communion. It’s not up to me to judge them, I’ll leave that to God.”

He urged politicians at Westminster, which reserves the power over abortion law, to overthrow the legislation.

Catholic voters, meanwhile, should consider “all the views” of those seeking election. MSPs, he said, should refuse to allow health services to participate in the “wanton killing of the innocent”. The Cardinal called on universities and medical schools to teach that “all human life” deserved protection. He also claimed that abortion had become an alternative form of birth control for many women. “Abortions to save the life of a woman are almost unheard of. As a society we wilfully ignore these realities.”

His remarks came two days after figures showed that the number of abortions carried out in Scotland rose to 13,081 in 2006, up from 12,603.

The Cardinal’s comments attracted heated criticism from politicians, pro-choice organisations and secularists.

The Green MSP Patrick Harvie said: “The issue of whether politicians who vote for abortion should receive Mass is entirely a matter for the Church, but to argue that anyone else in society who has a different view should be required to live by the Cardinal’s rules is absurd. To say that we should roll back 40 years of sexual and reproductive health care is ludicrous.”

The Liberal Democrat MSP Jeremy Purvis, who worked with David Steel, now Lord Steel of Aikwood, to draw up the original abortion legislation, said: “The Cardinal’s tone is both inflammatory and extreme. It’s very unfortunate he has chosen to use a hectoring and bullying tone against MSPs and MPs.”

Terry Sanderson, president of the National Secular Society, branded the remarks “undemocratic and unacceptable”. He said: “There is an implied call to Catholic politicians and health workers to place Catholic doctrine above the wishes of the electorate.”

Ann Furedi, chief executive of the British Pregnancy Advisory Service, said: “Abortion is essential in safeguarding women’s reproductive health. Women should be able to make their own choices.”

But Michael McMahon, Labour MSP for Hamilton North and Bellshill, said: “All he has done is reiterate a 2007-year-old Church position. It’s just canon law.”