In response, Labour's Clare Short accused the Scottish Catholics of doing the same thing to prevent MPs from speaking out in favour of choice on the issue.
The new controversy will further inflame the controversy, which anti- abortion activists are determined to highlight during the general election campaign.
The newly formed Pro-Life Alliance Party is planning to field candidates in areas where no representative of any other party is prepared to speak out against abortion. Its leaders say that they would like to contest 50 seats.
Last weekend, the head of the Catholic Church in England and Wales, Cardinal Basil Hume, described abortion as "a great evil in our society", and said the Church would never change its attitude to it.
Cardinal Thomas Winning, his Scottish equivalent, added yesterday that as Labour was basically pro-abortion, MPs who were not in line with its views were under pressure.
Tony Blair's stance on abortion is that while he is not in favour of it himself, he does believe that it is a matter for individual MPs.
Cardinal Winning said: "It's not Tony Blair's private opinion about abortion, it's the perception of the Labour Party's attitude towards abortion, which is very strongly pro-abortion and always has been.
"I have had too many Labour MPs tell of the pressures they are under to go along with the party line and if they didn't, they would lose their sponsorship from the trade unions - I can vouch for that. There is great pressure on them to be pro-abortion," he said.
Ms Short, Labour's overseas aid spokeswoman, has accused the Catholic Church of alienating a whole generation of women by failing to face up to the problems of sex. She said yesterday that the cardinal's views were "very sad".
"We know that the Catholic Church in Scotland has traditionally exerted unfair pressure on MPs on this issue. In the Labour Party we argue over these issues. We have a policy on these issues and we have an absolute right to conscience for Labour MPs and that is how it should be," she said.
A Labour spokeswoman said: "The issue of abortion should be a matter of individual conscience and not party politics."
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