Anne Brolly, who left the party two years ago after Sinn Féin changed its policy to allow terminations in cases of fatal foetal abnormalities, will visit Westminster with a group of pro-life activists including the DUP MLA Carla Lockhart.
The rally is being rganised by the group Both Lives Matter NI.
The protest comes two months after the Republic’s referendum to liberalise its abortion legislation – which has intensified pressure to amend the north’s restrictive laws.
Ms Brolly described her former party’s changed stance as an “abuse of power to make anyone say or do anything that goes against their conscience”.
Abortion is only legal in the north in cases where the woman’s life is at risk or there is a permanent or serious risk to her mental or physical health.
Tomorrow’s event has been described by organisers as a move to “to make sure the views of many women across Northern Ireland are heard”.
They also say that imposing new abortion laws from Westminster “will cripple the devolution settlement”.
Dawn McAvoy, one of co-founders of the Both Lives Matter, told the Irish News last month that the Republic’s landslide vote was a “wake-up call” for “so many people” in Northern Ireland.
“Irish people have made an overwhelming decision and we respect that. But we also want to educate so that a women in crisis doesn’t just feel she has no other option but an abortion,” she said.