Dr Martin Luther King's niece Alveda King and crossbench peer Lord Alton were among the speakers at the March for Life UK 2020, which was held online over the weekend due to coronavirus concerns.
In a powerful video message from the US, evangelist Alveda King spoke of how she was not always pro-life and had lost a child to abortion herself before becoming a Christian in 1983.
"When I became a Christian in 1983, my eyes were opened to the truth about abortion, about what a woman chooses when she chooses abortion," she said.
"She is choosing the death of her own child; we can't pretend it's anything less. We can never accept that this is ever the right course of action, even if a child has been diagnosed with a serious illness or a disorder like Down's syndrome."
She said British abortion laws allowing abortion up to birth for babies with disability was "heartbreaking", as she criticised the lack of legal protections for the unborn.
"Even children with disabilities are made in God's image and they deserve the same right to life as all of us," she said.
"Great Britain is celebrating the 10th anniversary of the Equality Act, which is supposed to advance the equality and opportunity for all. Those are nice words and equality is certainly a just cause but there's one group of people who are left out, whose equality does not matter ... the unborn.
"Many still deny the humanity of these babies even though we can see it with our own eyes on an ultrasound, even though we can hear with our own ears their hearts beating as they remain nestled in their mother's womb.
"We cannot call ourselves a just society, any society, anywhere in the world, when we allow, embrace, sanction and sanctify the right to abortion. And the fate that befalls that baby torn from the womb impacts us all."
Lord Alton said that the 1967 Abortion Act, introduced to allow abortions in certain limited circumstances, has since become an "out of control abortion law", with one of the consequences being a "fundamental shift in how our society treats the unborn, who are now left with little or no rights".
He said that the number of abortions in the UK - 9 million since the Act was passed half a century ago, should serve as a "wake-up call to society".
"But right across the country, we're letting down women and babies in the womb," he said.
"We need a fundamental and radical re-think to ensure that both groups get the support that they so desperately deserve. Why? Because both lives matter."
He was critical of the UK Government's imposition of the most extreme abortion framework in Europe on Northern Ireland, despite strong regional opposition.
He called on pro-lifers in the province to contact their MLAs to express their opposition and ask that legislation be brought forward to repeal the "regressive" regulations.
"Another 100,000 lives could be saved over the next 50 years if this legislation were to be repealed," he said.
He concluded with a call to people across the UK stand up against unjust laws, saying that the womb had "become the most dangerous place to be in Britain".
"We must move to a position where equality must begin from day one [of life]," he said.
"For the baby in the womb, life begins on day one, but if there are to be many more days in their lives and if one day there is to be change, you must become their guardian, you must become their advocate, you must become their voice, and you must get involved, get engaged and act."