Facebook is to ban ads relating to the Irish abortion referendum if they originate from outside the country.

The move is in response to fears that North American groups will try to influence the results of the referendum, to be held on May 25.

Ireland has some of Europe's most restrictive rules on abortion, which is illegal unless it is to save the life of a woman. However, moves to legalise terminations have been gaining traction, aided by the drastic decline in influence and popularity of the Catholic Church in the country as a result of revelations about longstanding abuse scandals.

US-based anti-abortion groups have begun buying ads aimed at influencing Ireland to vote 'no' to changing the law. While foreign ads on social media are not illegal in Ireland, Facebook said it would begin rejecting ads from outside the country on Tuesday. It said in a statement: 'As part of our efforts to help protect the integrity of elections and referendums from undue influence, we will begin rejecting ads related to the referendum if they are being run by advertisers based outside of Ireland.'

It said: 'We feel the spirit of this approach is also consistent with the Irish electoral law that prohibits campaigns from accepting foreign donations.'

The statement said: 'We understand the sensitivity of this campaign and will be working hard to ensure neutrality at all stages. Our goal is simple: to help ensure a free, fair and transparent vote on this important issue.'

Facebook has been under fire over its lack of transparency following the revelations that Cambridge Analytica harvested its data to inform Russian political advertising during the US presidential election.

It has introduced a new tool in Ireland enabling users to see all the ads released by a particular advertiser, rather than just the ones aimed at them. They will be able to see which ads result from shares by friends or their wider network and which are from paid campaigning.