Peter Lynas has called the proposed law change - that would legalise abortions in Northern Ireland for up to 28 weeks - a "travesty."
Currently, abortions are only allowed there under limited circumstances.
Speaking at the event Peter said: "[The proposed law] is an absolute travesty and it was forced upon us without proper consultation or proper regulations to put it in place. It's just bad law.
"100,000 people are alive in Northern Ireland because we don't have that law, we don't want that to change. We want to be a beacon of hope and a beacon of light instead."
On 10th July Westminster MPs and Peers voted to add amendments to Northern Ireland's (Executive Formation) Bill that would introduce more extreme laws on abortion, unless the Assembly - which has not been functioning properly for the past two years - is restored by 21st October.
The bill would mean that an abortion would be legal up to nearly 7 months into a pregnancy, under any circumstances, a decision that many campaigners say is not in line with the public opinion of NI.
On Friday evening, 20,000 anti-abortion protesters stood in silent protest to defend those "who have no voice" and call on the government to put a stop the proposed law that would give NI the most liberal abortion laws in Europe.
Leader of Northern Ireland's Democratic Unionist Party and devout Christian Arlene Foster, showed her support for the pro-life campaigners.
Posting on social media she said: "Joining thousands to stand together and defend the rights of the unborn child. Both lives matter."
At the @NIvoiceless protest. Joining thousands of people from across all backgrounds tonight, to stand together and defend the rights of the unborn child. Both lives matter. pic.twitter.com/k8XVvlCZ1B— Arlene Foster (@DUPleader) September 6, 2019
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