Britain's largest abortion provider has sought a High Court ruling to make it easier for women to complete the procedure at home.
The British Pregnancy Advisory Service (BPAS) wants an updated interpretation of the 1967 Abortion Act to allow women to take the second dose of tablets for an early medical abortion (EMA) at home.
At present, the first and second dose must be taken in a clinic or hospital under supervision. Most women go straight home after the second dose.
BPAS says the UK should follow other countries, including the US, France and Sweden, in allowing women to safely complete their terminations without repeated visits to a clinic.
The Department of Health will contest the legal action, scheduled for January 28, while pro-life campaigners said BPAS' intention was to make abortion "little more than a pill-popping exercise".
An EMA can be used up to nine weeks' gestation and involves receiving pills in two stages.
On the first visit, women swallow one mifepristone tablet and are told to return to the clinic 24 to 48 hours later.
Women then receive a dose of four tablets (misoprostol), which are usually inserted vaginally, can be swallowed or are dissolved under the tongue or between the cheek and the gum.
Cramping and bleeding to bring about a miscarriage usually begins one to two hours after this dose but can start sooner in some cases. The abortion is usually completed within four to six hours.
The legal challenge by BPAS comes after decade-long talks broke down between ministers and experts at the charity.
Ann Furedi, chief executive of BPAS, said it could no longer "sit back" on the issue after a decade of "ebbing and flowing of enthusiasm" within Government.
Such enthusiasm has been "entirely dependent" on whether officials deemed it "politically expedient" for reform of abortion services to take place, she said, adding that the Department had always agreed it was safe for women to complete abortions at home.
BPAS argues that women suffer unnecessary anxiety about having an abortion on their way home from the clinic, especially those who have travelled long distances or who use public transport.
Dr Patricia Lohr, medical director of BPAS, said a second visit to the clinic is "medically unnecessary".
She added: "Most women prefer to go home because it's a private setting, it's comfortable, they can have their friends with them, they can have their family with them, they can have their partner."
Ms Furedi said the legal action would not alter who could get an abortion but would simply mean that those who were entitled to one could complete the procedure in their own homes.
Studies show that women who take the second dose at home have the same outcomes as those given it in a clinic, with no difference in, for example, the number of incomplete abortions.
A 24-hour helpline is available for any concerns and women can attend a clinic for urgent medical treatment if needed, said Ms Furedi.
Those who wish to stay in the clinic - very small numbers at present - will be able to do so, she added.
Ms Furedi said BPAS simply wanted to see a "minor change" to the interpretation of the law, adding it was about how the word "treatment" was understood legally.
The 1967 Abortion Act stipulates that treatment for the termination of pregnancy must be carried out in a hospital or clinic.
Ms Furedi said the charity resented being prevented from providing the best service to patients by "needless bureaucracy".
Kelly Culwell, senior abortion adviser at the International Planned Parenthood Federation (IPPF), said home use of the medication had become routine in India, Ethiopia, North Korea, France and the United States.
The pro-life group, the Society for the Protection of Unborn Children (SPUC), said it would seek to intervene in the case.
A statement from the charity Life said: "This has shifted the debate away from whether or not a woman has an abortion at all, simply to how and where she does it."
A spokeswoman for the Department of Health said it was a matter for the courts to decide.
"However, it is the Government's view that the words 'any treatment for the termination of pregnancy' under Section 1(3) of the Abortion Act 1967 cover both the prescription and the administration of the drugs used in abortion," she said.
"In the Government's view, this means that both tablets used for medical abortion must be administered on premises which have been approved under the Abortion Act. For this reason, the Government is contesting this case."