Christian Concern is mounting a legal challenge against changes to abortion regulations brought in by the Government during the coronavirus crisis.
The Government first announced on its website on March 23 that it would permit DIY abortions during the lockdown.
The information was subsequently removed from the web page with a message in its place saying that the changes had been posted "in error".
A day later, health secretary Matt Hancock said that there were no proposals on the table to change abortion rules due to Covid-19.
This position remained when the Coronavirus Bill was brought before the House of Lords on March 25, with health minister Lord Bethell rejecting proposed changes to the abortion law on behalf of the Government.
He stated at the time: "We do not agree that women should be able to take both treatments for medical abortion at home. We believe that it is an essential safeguard that a woman attends a clinic, to ensure that she has an opportunity to be seen alone and to ensure that there are no issues."
Despite this, the Government confirmed on Monday that it had relaxed the rules to allow women and girls to take two abortion pills at home up to 10 weeks after consulting a doctor over the phone or through video link.
Christian Concern called it an "incredible double U-turn" and "the most significant change to abortion law since 1967".
It is launching a judicial review of the decision to change the rules without proper parliamentary scrutiny.
Christian Concern chief executive, Andrea Williams, said that the Government had "acted unlawfully", as she echoed the fears of former Supreme Court Justice Lord Sumption, who warned of an increasing "police state" during the lockdown.
She further warned that the changes remove an important safeguard to prevent women from being pressured into abortions.
"We are meant to be living in a democracy. In this case, the Government announced a change, then backtracked and claimed this was an error, then explained to parliament that there would be no changes, and then backtracked again and changed the law anyway. This is not how democratic governments are supposed to act," she said.
"The Government is meant to be acting to protect lives due to the threat of Covid-19. Instead it has acted to make it easier for women to be pressured into ending lives. It has done this in a disgraceful underhand manner.
"The coronavirus crisis is being exploited to make changes to the law which would not be possible if parliament was functioning properly."
She added: "This is nothing less than a fight to preserve our hard-won democratic freedoms which do not allow the government to make changes to the law on a whim with no accountability."
Pro-life group, the Society for the Protection of Unborn Children (SPUC), has said it is also looking into a judicial review into the Government's actions.
"It is our understanding that such a policy is beyond the scope of the Abortion Act. However, we will closely examine the policy and take appropriate action based on the best legal advice," said SPUC's deputy CEO John Deighan.
He was scathing of the Government's handling of the issue in the last week, calling it an "utter fiasco".
"What we are witnessing is a shambolic and rudderless Government which has made no less than three contradictory statements in a matter of days," he said.