The Society for the Protection of Unborn Children (SPUC) is taking legal action against Westminster over a "devolution power grab" over Northern Ireland's abortion laws.
The pro-life group is raising £100,000 to fund the case, which is expected to be heard at the High Court later in the year.
It is challenging new regulations handing Northern Ireland Secretary Brandon Lewis the power to direct Stormont ministers on implementing a "fully-funded abortion service" over the heads of MLAs.
SPUC questions the "validity and lawfulness" of the regulations, and wants the High Court to declare them "of no force or effect".
It also wants the court to rule that NI ministers are under "no obligation to comply with any direction issued by the Secretary of State under the 2021 regulations".
Liam Gibson, SPUC's NI Political Officer, called Westminster's actions "disgraceful", and said the regulations were "illegitimate and unconstitutional".
"If allowed to stand it will not only condemn to death an untold number of unborn babies but fatally undermine the devolution settlement as well," he said.
"By seizing power over our abortion laws, London is stripping locally elected Ministers of power and have denied the people an accountable government with a democratic mandate.
"These regulations give unprecedented power to a politician who is not answerable to the people of Northern Ireland.
"It is a basic principle of democracy that politicians are accountable to the electorate."
He added, "We are calling for all pro-life voices to unite in backing this case. The politicians making the decisions about our abortion laws must be accountable to the people of Northern Ireland.
"This is essential if full legal protection for unborn children is ever to be restored."
John Deighan, SPUC's deputy CEO said: "These are the most challenging times the pro-life movement has ever faced in Northern Ireland.
"We also need the prayers of pro-life supporters and their financial assistance too as we seek to raise the funds required to finance the court case."