The High Court has begun to hear arguments on whether it should be easier for women to complete pregnancy terminations at home.
Yesterday, the UK's biggest abortion provider, the British Pregnancy Advisory Service (BPAS) began its bid to overturn current practice, and urged a judge to rule the 1967 Abortion Act allows women to take the second dose of tablets for an early medical abortion (EMA) without having to visit medical premises.
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.
Nathalie Lieven QC, appearing for BPAS, said "medical science has moved on a great deal" and it was safe for women to self-administer the second dose at home.
Ms Lieven asked Mr Justice Supperstone, sitting at London's High Court, to rule against Health Secretary Andrew Lansley, who says that the law requires all tablets to be administered on clinical premises.
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.
Ant-abortion campaigners say BPAS's intention is to make abortion "little more than a pill-popping exercise".
The Society for the Protection of Unborn Children (SPUC) has been given permission to put its views to the judge.
In 2009, around 70,000 early medical abortions were carried out below nine weeks in England and Wales, accounting for about half of all early abortions.
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.
BPAS argues women suffer unnecessary anxiety about having an abortion on their way home from the clinic after taking the second dose of tablets, especially those who have travelled long distances or who use public transport.
The potentially landmark case requires the judge to decide the meaning of the words 'any treatment for the termination of pregnancy' under Section 1(3) of the Abortion Act 1967 and whether they cover both the prescription and the administration of the drugs used in abortion.
The Government's interpretation means that the administration of both sets of abortion tablets amounts to "treatment" which must be carried out by a "registered medical practitioner" on premises which have been approved under the Abortion Act.
The hearing continues later next week.