It is the clearest signal yet that church leaders are ready to oppose any moves to relax abortion law in Scotland.
In a letter which will be read in all of Scotland’s 500 parishes this weekend, Catholics will be told that they should consider “joining a political party instead of leaving it to others to determine the future of Scotland”
The letter on behalf of Scotland’s eight bishops will set out how the Scottish Parliament is to gain several extra powers including “responsibility for legislation regarding abortion in Scotland”.
Pro-choice groups have already launched a campaign to change the law in Scotland on abortion when Holyrood takes control. They say it should no longer be a criminal offence unless two doctors approve the procedure.
There have been no moves yet to relax the current 24 week time limit for a termination, but such a development is likely to be met with fierce resistance from the Catholic Church.
The letter states: “It is the duty of every catholic to try to influence society for the better.”
It adds: “Please bring to this election the benefits of the insight that your Christian faith gives: insight into the dignity of each person, particularly the weakest and most vulnerable; insight into the value of all human life from conception to natural death; insight into the family as the fundamental unit of our society.”
The bishops urge followers to “make their views known” to the candidates and the parties.
Detailed advice is given about the two votes Scots have in the election as part of the first past the post and regional list.
The constituency vote allows voters to have “a direct say” in who is elected.
“So scrutinise the candidates so as to vote for the person most compatible with your views,” it adds.
The second vote, it explains, is for a political party which “controls who is on their list”.
The Bishops add: “This is a concern when it comes to matters of conscience, where parliament may give a free vote to MSPs.
“It is important, therefore, that you seek to influence political parties by making your views known to them.”
The letter is signed by all eight of Scotland’s Bishops, including Philip Tartaglia, President of the Conference and effectively the head of the Catholic Church in Scotland.
But a spokeswoman for the British Pregnancy Advisory Service (bpas) said polling shows most Catholics support access to “safe, legal abortion and contraception”.
She added: “1 in 3 women will have an abortion during their lifetime. For those women abortion is not an abstract issue but a part of their history. As abortion is devolved to Scotland our hope is that women and their loved ones feel empowered to speak out.”